anestesi labor & delivery

8/6/2019 Anestesi Labor & Delivery

1/20

Regional Anesthesia and Analgesia for Labor andDelivery

Holger K. Eltzschig, M.D., Ellice S. Lieberman, M.D., Dr.P.H., and William R.

Camann, M.D.

In 1847, the Scottish obstetrician James Simpson administeredether to a woman during

labor to treat the pain of childbirth. He was impressed

with the degree of analgesia associated withthe use of the

drug. Nevertheless, he expressed concern aboutthe possible adverse effects of anesthesia:"It will be necessaryto ascertain anesthesia's precise effect, both upon the action of the

uterus and on the assistant abdominal muscles; its influence, if any, upon the child;

whether it has a tendency to hemorrhageor other complications."1

One and a half centuries later, the maternal and fetal effectsof analgesia during labor

remain central to discussions amongpatients, anesthesiologists, and obstetricalcaregivers. A numberof randomized trials have sought to address the effects of different

strategies for analgesia on maternal and fetal outcomes. Despite this effort, it has becomeincreasingly clear that potentiallyunwanted effects of analgesia for women in labor and

their childrencannot be determined easily. Remaining controversies in obstetrical

anesthesia include that over the effects of regional anesthesia on the progress andoutcome of labor, as well as that over itseffects on the neonate. In this article we will

concentrateon advances in the administration of epidural, spinal, or combinedspinal

epidural analgesia during labor. However, thereare many other methods of painmanagement that may be chosenby women in labor, such as opioids,2 hydrotherapy,

hypnotherapy,the use of labor-support personnel (doulas), massage, movement and

positioning, and sterile-water blocks, among others.3

These

alternative methods can beused successfully either alone orin conjunction with epidural analgesia. In addition,successfulrelief of labor pain in itself is not necessarily associatedwith high levels of

satisfaction on the part of parturient women.4,5Factors such as the woman's involvement

in decision making,social and cultural factors, the woman's relationship with hercaregivers, and her expectations regarding labor may be equally,if not more, important.

Regional Analgesia for Vaginal Delivery

Technique of Regional Analgesia

Approximately 60 percent of women, or 2.4 million each year,choose epidural orcombined spinalepidural analgesiafor pain relief during labor.6Labor pain is transmitted

throughlower thoracic, lumbar, and sacral nerve roots (Figure 1 andFigure 2) that areamenable to epidural blockade. Epidural analgesiais achieved by placement of a catheter

into the lumbar epiduralspace. Solutions of a local anesthetic, opioid, or both canthen be

administered as intermittent rapid doses or as a continuous infusion (Figure 3). Thealternative technique of combined spinalepiduralanalgesia has recently gained in

popularity. With this technique,a single bolus of an opioid, sometimes in combination
http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R1%23R1http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R1%23R1http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R2%23R2http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R3%23R3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R3%23R3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R4%23R4http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R4%23R4http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R5%23R5http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R5%23R5http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R6%23R6http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R6%23R6http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F1%23F1http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F2%23F2http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F2%23F2http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F3%23F3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R2%23R2http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R3%23R3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R4%23R4http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R5%23R5http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R6%23R6http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F1%23F1http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F2%23F2http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F3%23F3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R1%23R1


2/20

with localanesthetic, is injected into the subarachnoid space, in additionto the placement

of an epidural catheter (Figure 3). The useof a subarachnoid bolus of opioids results in

the rapid onsetof profound relief of pain with virtually no motor blockade. In contrast toepidural local anesthetics, spinal opioids donot cause impairment of balance, giving the

parturient womanthe option to continue ambulation.7Combined spinalepiduralanalgesia

is associated with a higher degree of satisfaction

among parturient women than isconventional epidural analgesia.8However, some studies have suggested that there may

be an increasein the frequency of nonreassuring patterns in the fetal heart rate,

particularly bradycardia, with combined spinalepiduralanalgesia, and such patterns maynecessitate emergency cesareandelivery.9,10,11 Other studies show no difference in the

fetalheart rate and no increase in the rate of cesarean deliveriesnecessitated by fetal

bradycardia.12,13Although there are insufficientdata to establish whether there is a causal

association, itis reassuring that no studies suggest that combined spinalepiduralanalgesia is associated with an increase in adverse outcomes for the fetus.

View larger version

(87K):[in this window]

[in a new window]

Figure 1. Pathways of Labor Pain.

Labor pain has a visceral component and a somatic component.

Uterine contractions may result in myometrial ischemia, causingthe release of potassium, bradykinin, histamine, and serotonin. In

addition, stretching and distention of the lower segments of the

uterus and the cervix stimulate mechanoreceptors. These noxious

impulses follow sensory-nerve fibers that accompany sympatheticnerve endings, traveling through the paracervical region and the

pelvic and hypogastric plexus to enter the lumbar sympathetic

chain. Through the white rami communicantes of the T10, T11,T12, and L1 spinal nerves, they enter the dorsal horn of the spinal

cord. These pathways could be mapped successfully by ademonstration that blockade at different levels along this path(sacral nerve-root blocks S2 through S4, pudendal block,

paracervical block, low caudal or true saddle block, lumbar

sympathetic block, segmental epidural blocks T10 through L1, andparavertebral blocks T10 through L1) can alleviate the visceral

component of labor pain.
http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F3%23F3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R7%23R7http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R7%23R7http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R8%23R8http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R8%23R8http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R9%23R9http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R9%23R9http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R10%23R10http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R11%23R11http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R11%23R11http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R12%23R12http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R12%23R12http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R13%23R13http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R13%23R13http://content.nejm.org/cgi/content/full/348/4/319/F1http://content.nejm.org/cgi/content-nw/full/348/4/319/F1http://content.nejm.org/cgi/content/full/348/4/319/F1http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#F3%23F3http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R7%23R7http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R8%23R8http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R9%23R9http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R10%23R10http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R11%23R11http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R12%23R12http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R13%23R13http://content.nejm.org/cgi/content/full/348/4/319/F1http://content.nejm.org/cgi/content-nw/full/348/4/319/F1


3/20

View larger version

(34K):

[in this window]

[in a new window]

Figure 2. Labor Pain during Different Stages of Labor.

Traditionally, labor has been divided into three stages. The first

stage is defined as that lasting from the start of regular uterine

contractions until the completion of cervical dilatation. It is

commonly subdivided into a latent and an active phase, the latterbeing characterized by a rapid acceleration of cervical dilatation.

The second stage proceeds from the first stage until the delivery ofthe fetus is complete, and the third stage continues until the

placenta and membranes have been expelled. Pain during the first

stage of labor is visceral and is therefore mediated by the T10through L1 segments of the spine, whereas during the later part of

the first stage and throughout the second stage, an additional

somatic component is present, mediated by the S1 through S4segments of the spine. Active pain pathways are marked in red.

View larger

version (76K):

[in this window]

[in a new window]

Figure 3. Technique of Epidural Analgesia and Combined Spinal

Epidural Analgesia.

Epidural analgesia (Panel A) is achieved by placement of a catheter

into the lumbar epidural space (1). After the desired intervertebralspace (e.g., between L3 and L4) has been identified and infiltrated

with local anesthetic, a hollow epidural needle is placed in the

intervertebral ligaments. These ligaments are characterized by a highdegree of resistance to penetration. A syringe connected to the

epidural needle allows the anesthesiologist to confirm the resistance

of these ligaments. In contrast, the epidural space has a low degree ofresistance. When the anesthesiologist slowly advances the needle

while feeling for resistance, he or she recognizes the epidural spaceby a sudden loss of resistance as the epidural needle enters the

epidural space (2). Next, an epidural catheter is advanced into thespace. Solutions of a local anesthetic, opioids, or a combination of

the two can now be administered through the catheter.

For combined spinalepidural analgesia (Panel B), the lumbarepidural space is also identified with an epidural needle (1). Next, a

very thin spinal needle is introduced through the epidural needle into

the subarachnoid space (2). Correct placement can be confirmed by

free flow of cerebrospinal fluid. A single bolus of local anesthetic,

opioid, or a combination of the two is injected through this needleinto the subarachnoid space (3). Subsequently, the needle is removed,

and a catheter is advanced into the epidural space through theepidural needle (4). When the single-shot spinal analgesic wears off,

the epidural catheter can be used for the continuation of pain relief.

Effect of Epidural Analgesia on the Method of Delivery
http://content.nejm.org/cgi/content/full/348/4/319/F2http://content.nejm.org/cgi/content-nw/full/348/4/319/F2http://content.nejm.org/cgi/content/full/348/4/319/F3http://content.nejm.org/cgi/content-nw/full/348/4/319/F3http://content.nejm.org/cgi/content/full/348/4/319/F3http://content.nejm.org/cgi/content/full/348/4/319/F2http://content.nejm.org/cgi/content/full/348/4/319/F2http://content.nejm.org/cgi/content-nw/full/348/4/319/F2http://content.nejm.org/cgi/content/full/348/4/319/F3http://content.nejm.org/cgi/content-nw/full/348/4/319/F3


4/20

The use of epidural analgesia is associated with better pain relief than are systemic

opioids.14,15,16,17 However, a majorconcern is whether epidural analgesia may be

responsible foran increased risk of cesarean delivery, vaginal delivery requiringthe useof forceps or vacuum extraction, or prolongation oflabor. Both cesarean deliveries and

instrument-assisted vaginaldeliveries may be associated with a greater risk of maternal

complications than unassisted vaginal delivery. Although the

appropriate rate of cesareandelivery remains a matter of debate18(currently in the United States, the babies of 23

percent ofpregnant women are delivered by cesarean section19), there isgreat interest in

the effect of epidural analgesia on theserates. In addition, the rate of instrument-assistedvaginaldelivery is of concern because it is consistently associatedwith a higher rate of

serious perineal laceration,20 which hasbeen implicated as a risk factor for later fecal

incontinence.21Instrument-assisted vaginal deliveries have also been linkedto higher rates

of birth injuries.22

Observational Studies

Many studies compare women who selected epidural analgesia with

those who did not.Most such studies show an association between the use of epidural analgesia and a higher

rate of cesareandelivery. However, women who select epidural analgesia are differentfrom those who do not. They are more frequently nulliparous,come to the hospital earlier

in the course of labor with the fetus having descended to a lesser degree (a higher fetal

station),have slower cervical dilatation, deliver larger babies, and have smaller pelvicoutlets.23,24,25,26 Observational studiesthat control for these factors continue to find

differencesin outcome between the women who receive epidural analgesiaand those who

do not.24,26 One observational study suggeststhat women with difficult labor may have

more pain early inlabor and require a more potent regimen for pain relief. 27

However, although the small subgroup of women with exceptionally

painful labor may bemore likely to choose epidural analgesia,this is clearly not the main factor contributing to

the choiceof a method of pain relief, since many women having a firstbaby decide before

labor whether to receive epidural analgesia.28Overall, given the possibility ofuncontrolled confounding,it is not possible to draw definitive conclusions from these

observational studies.

Randomized Trials

Prospective, randomized trials studying the relation betweenthe use of epidural analgesiaand cesarean delivery have shownvariable results. A recent meta-analysis represents the

experienceof nearly 2400 patients randomly assigned to receive eitherepidural analgesia

or parenteral opioid analgesia.17Epiduralanalgesia was associated with a prolongation ofthe first stageof labor by an average of 42 minutes and a prolongation of thesecond stage

of labor by an average of 14 minutes. No significant difference between groups in the rate

of cesarean delivery couldbe demonstrated by intention-to-treat analysis (8.2 percentof

women in the epidural group had cesarean deliveries, as comparedwith 5.6 percent in theparenteral-opioid group).
http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R14%23R14http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R14%23R14http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R15%23R15http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R15%23R15http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R16%23R16http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R16%23R16http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R18%23R18http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R18%23R18http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R19%23R19http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R20%23R20http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R21%23R21http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R21%23R21http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R22%23R22http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R22%23R22http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R23%23R23http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R23%23R23http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R24%23R24http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R24%23R24http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R25%23R25http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R25%23R25http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R26%23R26http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R24%23R24http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R24%23R24http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R26%23R26http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R27%23R27http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R27%23R27http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R28%23R28http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R28%23R28http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R14%23R14http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R15%23R15http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R16%23R16http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R18%23R18http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R19%23R19http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R20%23R20http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R21%23R21http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R22%23R22http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R23%23R23http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R24%23R24http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R25%23R25http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R26%23R26http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R24%23R24http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R26%23R26http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R27%23R27http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R28%23R28http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17


5/20

However, in most of the large studies, about 30 percent of womendid not receive the

treatment to which they were assigned. Many women assigned to the parenteral-opioid

group actually receivedepidural analgesia, and many women assigned to receive epiduralanalgesia did not receive it. When such crossover occurs, theproportion of women who

receive epidural analgesia in the twogroups becomes much more similar, making it very

difficult to

interpret the data on an intention-to-treat basis. In many trials,

a substantialproportion of women did not receive the assignedtreatment because delivery occurred so

rapidly that there wasno time to administer any analgesia. In addition, women whoagree

to be randomly assigned to a certain form of pain reliefduring active labor may representa subgroup of women with lessdifficult labors or other characteristics that render them

unrepresentativeof the general population. This high rate of noncompliance withthe

protocols limits our ability to interpret the data.29

There have been two randomized trials with essentially no crossover. In the first trial, inwhich 93 nulliparous women in spontaneouslabor at term were randomly assigned to

epidural analgesia orparenteral meperidine, essentially all women received the assigned

treatment. This study found a large effect of the use of epidural

analgesia on the rate ofcesarean deliveries performed becauseof dystocia (17 percent in the epidural group vs. 2percentin the meperidine group).30 In contrast, a more recent study,31in which 459

nulliparous women in active labor were randomlyassigned to either epidural analgesia or

intravenous meperidineand in which 8 percent of the subjects had protocol violations,found no significant difference in the rate of cesarean deliveriesperformed because of

dystocia (6 percent in the epidural group vs. 7 percent in the meperidine group).

It is not clear why these two studies had such different results.It is important to note that

the effect of epidural analgesiaon the likelihood of cesarean delivery may vary accordingtoobstetrical practice and the population studied and that suchvariations may be the

reasons for the differences between the

studies.

32,33

Studies have clearly demonstratedgreat variationsin physician-specific rates of cesarean delivery, suggestingthatmanagement practices may have an important role. For example,in a study of 1533

parturient women who were cared for by 11obstetricians, the rate of cesarean delivery

varied from 19percent to 41 percent for different caregivers.33 In addition,womenenrolled in many of the randomized trials were much youngerthan the general population

of women delivering babies in theUnited States.34 Studies consistently demonstrate an

increasein the rate of cesarean delivery associated with age,35 andthe effect of epidural

analgesia may vary with age as well. Therefore, the question of whether the use ofepidural analgesiafor pain relief during labor increases the rate of cesareandeliveries

performed because of a failure of labor to progressremains unanswered.

Findings with regard to an association between instrument-assistedvaginal delivery andepidural analgesia are clearer, with aconsistent increase in the rates of deliveries

involving forcepsand vacuum extraction with epidural analgesia. The meta-analysisof

randomized trials found a doubling of the rate of instrument-assistedvaginal deliveries.17

The most recent randomized trial foundan increase in the rate of deliveries involvingforceps from3 percent in the opioid group to 12 percent in the epidural-analgesiagroup.31

However, the reason for this increase with epidural analgesia remains unclear. One
http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R29%23R29http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R29%23R29http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R30%23R30http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R31%23R31http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R31%23R31http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R32%23R32http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R32%23R32http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R34%23R34http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R35%23R35http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R31%23R31http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R29%23R29http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R30%23R30http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R31%23R31http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R32%23R32http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R34%23R34http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R35%23R35http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R31%23R31


6/20

hypothesis is that the motorblockade may prevent the mother from pushing and thereby

necessitatethe use of instruments. Epidural analgesia is also associatedwith a higher

frequency of the occiput posterior position ofthe fetus at delivery, which, if causal, couldrepresent a mechanismby which epidural analgesia contributes to the higher rate of

instrument-assisted delivery.30,36,37It is also possible thatthe presence of an epidural block

may sometimes decrease the

obstetrician's threshold for performing instrument-assisteddeliveries,17 as well as for allowing instrument-assisted deliveryfor the purposes of

teaching residents.37

Studies of Sentinel Events

A different approach is taken to the question of epidural analgesiaand cesarean delivery

by studies comparing the rates of cesarean delivery before and after epidural analgesiawas made availablefor a certain population of women. The assumption of such studiesis

that the population of women, the obstetrical managementstyle, and other confounding

variables change little over time.None of these studies have demonstrated an increase in

the rate

of cesarean delivery associated with the sudden availability

of epiduralanalgesia.38,39,40,41,42 A recent meta-analysisof these studies, which included more than

37,000 patients ina variety of different practice settings and time periods inseveralcountries, showed that the establishment of a highlyutilized epidural-analgesia service

had no effect on the overallincidence of cesarean delivery or the rate of cesarean

deliveriesperformed because of dystocia.43

However, these studies have methodologic limitations. First,it is almost impossible tocontrol for changes in practice stylethat may occur when an epidural-analgesia service is

introduced;such changes may be made specifically because providers areaware of the

potential association of epidural analgesia withan increased rate of cesarean deliveries.

Second, there may

be secular trends, such as overall changes in the rate of cesareandelivery between the two periods being studied. Finally, substantialchanges may occur in

the rate of cesarean delivery in subgroups of patients (e.g., nulliparous women in

spontaneous labor) withoutcausing a statistically detectable increase in the overall rateofcesarean delivery. It would be difficult with this type ofstudy design to detect changes

even in large subgroups of women.Therefore, these studies do not provide a conclusive

answerto the question of the effects of epidural analgesia on outcomesof labor forindividual women. However, they do show that theinstitution of an active anesthesia

service providing epiduralanalgesia need not lead to an increase in the overall rate of

cesarean delivery.

In summary, it appears that epidural analgesia may prolong labor by approximately onehour, on average.The effect on the rateof cesarean delivery is unclear and may vary with

the practice-relatedchoices of the provider.29,32,33 The literature does provideevidence of

an increase in the rate of instrument-assisted vaginaldelivery and a decrease in the rate ofspontaneous vaginal deliverieswith epidural analgesia, although the reason for this

associationis not well understood, and the magnitude of the association may be

influenced by the practice style of the obstetrician.
http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R30%23R30http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R30%23R30http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R36%23R36http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R36%23R36http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R37%23R37http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R37%23R37http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R37%23R37http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R37%23R37http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R38%23R38http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R38%23R38http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R39%23R39http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R39%23R39http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R40%23R40http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R40%23R40http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R41%23R41http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R41%23R41http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R42%23R42http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R43%23R43http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R43%23R43http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R29%23R29http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R29%23R29http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R32%23R32http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R32%23R32http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R30%23R30http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R36%23R36http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R37%23R37http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R17%23R17http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R37%23R37http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R38%23R38http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R39%23R39http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R40%23R40http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R41%23R41http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R42%23R42http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R43%23R43http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R29%23R29http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R32%23R32http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R33%23R33


7/20

Timing of Epidural Analgesia during Labor

It has been suggested that the effect of epidural analgesiaon labor and the method of

delivery may be greater when suchanalgesia is administered before a certain degree of

cervicaldilatation or a certain fetal station has been reached. Mostobservational studies

show higher rates of cesarean delivery

with early administration of epiduralanalgesia.26,44,45 Incontrast, the three randomized studies specifically comparingthe

initiation of epidural analgesia at different degrees ofcervical dilatation in nulliparous

women found no differencein the rate of cesarean delivery or instrument-assisted vaginaldelivery between women in whom analgesia was initiated early and those in whom it was

initiated late.46,47,48 However, thesmall degree of difference in cervical dilatation between

theearly and late groups (approximately 1 cm) is an important limitationof these trials.There is currently insufficient evidence todetermine whether waiting until a certain

degree of cervicaldilatation or a certain fetal station is reached before institutingepidural

analgesia will influence the rate of cesarean or instrument-assistedvaginal deliveries.

Effect of Combined SpinalEpidural Analgesia on the Rate ofCesarean Delivery

Since combined spinalepidural analgesia is not associatedwith impaired equilibrium,7

ambulation during labor can be continuedby up to 80 percent of parturient women.49 Itwas thereforehypothesized that the use of combined spinalepidural analgesia in

association with continued ambulation might lead to a decrease in the rate of cesarean

delivery. The resultsof major clinical trials did not support this hypothesis50 ora positiveeffect of ambulation itself on the rate of cesareandelivery.51However, a randomized trial

did demonstrate thatcombined spinalepidural analgesia is associated withmore rapid

cervical dilatation in nulliparous women than is conventional epidural analgesia, although

no difference in the

rate of cesarean delivery was found.52

Effect of Epidural Analgesia on Maternal Temperature and theNewborn

Epidural anesthesia in nonobstetrical patients is generallyassociated with a decrease inbody temperature. Epidural anesthesiacauses vasodilatation in the anesthetized

dermatomes, whichleads to a redistribution of heat from the core to the periphery,

resulting in a net decrease in body temperature.53In contrast,observational and

randomized studies demonstrate that epiduralanalgesia during labor is often associatedwith an increasein maternal body temperature to over 100.4F (38.0C).54,55,56For

example, in a randomized trial in which fever was reported,an additional 11 percent ofwomen receiving epidural analgesiabecame febrile during labor (15 percent, vs. 4 percentof womenwho received no epidural analgesia), and the proportion of thepopulation

affected was even greater among nulliparous women(24 percent vs. 5 percent).55An

association between the useof epidural analgesia and maternal fever raises someimportantquestions: Does epidural analgesia cause maternal or neonatalinfections? Do

children of mothers who receive epidural analgesia more frequently require evaluation for

sepsis and treatmentwith antibiotics?
http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R26%23R26http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R26%23R26http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R44%23R44http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R44%23R44http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R45%23R45http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R46%23R46http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R46%23R46http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R47%23R47http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R47%23R47http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R48%23R48http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R7%23R7http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R49%23R49http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R49%23R49http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R50%23R50http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R51%23R51http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R51%23R51http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R52%23R52http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R52%23R52http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R53%23R53http://content.nejm.org/cgi/content/full/348/4/319?SEARCHID=1080817185945_1834&hits=20&excludeflag=TWEEK_element&FIRSTINDEX=20&journalcode=nejm&sortspec=Score%2Bdesc%2BPUBDATE_SORTDATE%2Bdesc&andorexacttitleabs=and&fulltext=obstetric&andorexactfulltext=and&searchid=1080817239434_1847&FIRSTINDEX=20&journalcode=nejm#R53%23R53http://content.nejm.org/cgi/content/full/3

anestesi labor & delivery

Documents