Preterm Labor

Rationale

The reduction of preterm births remains an important goal in obstetric care.

Understanding the causes and recognizing the symptoms of preterm labor provides the basis for management decisions.

Preterm Labor

Definition

Labor prior to 37 weeks gestation (259 days)

Labor: presence of uterine contractions between 20-37 weeks gestation leading to cervical change

Dilation

Effacement

Station

Complicates 8-10% pregnancies

Preterm Birth

Any delivery occurring prior to 37 weeks

Incidence – 11% of live-births

1/3 of PTB due to spontaneous rupture of membranes

1/3 of PTB due to obstetrical causes

1/3 of PTB due to idiopathic preterm labor

Preterm Labor

Consequences

Severity and frequency increase as gestational age decreases

75% of perinatal deaths are associated with sequellae of preterm birth, including:

RDS

IVH

NEC

Sepsis

Neurologic deficits / seizures

Preterm Labor

Leads to preterm birth 40-50%

Most common cause of perinatal morbidity and mortality

In U.S., 8-10% of babies born prematurely account for 60-75% of all perinatal morbidity and mortality

Preterm birth accounts for 35% of all U.S. health care

spending for infants

Preterm Labor Potential causes

Idiopathic – most common

Dehydration

PROM – can be secondary to subclinical infection of fetal membranes

Infection

Cervical

Intraamniotic

Urinary

Preterm Labor

Potential causes

Excessive uterine enlargement

Polyhydramnios

Multiple gestation (1% pregnancies)

Uterine distortion

Leiomyomas

Müllerian anomalies

Placental anomalies

Previa

Abruption

Preterm Labor

Potential causes

Incompetent cervix

Substance abuse

Fetal anomalies

Iatrogenic

Induction of labor because of maternal or fetal health complication (such as severe preeclampsia)

Risk Factors

History of preterm labor and delivery If one early delivery, risk with next pregnancy: 2x

If two early deliveries, risk with next pregnancy: 3x

Smoking

Non-white

Low socioeconomic status

Uterine malformation

Vaginal infections

Pre-pregnancy weight <50 kg

Preterm Labor

Symptoms Menstrual-like cramps

Low, dull backache

Pelvic pressure

Abdominal cramping

Uterine contractions

Cervical dilation without feeling contractions

Vaginal bleeding

Preterm Labor

Evaluation EFM to monitor FHTs and frequency/duration

of contractions Strength of contraction cannot be assessed with

external monitors

Abdominal palpation by an experienced nurse can assess mild, moderate or severe contractions

Obtain cervical cultures Gonorrhea

Chlamydia

Group B Strep

Preterm Labor Evaluation

Assess cervical status

Dilation, effacement, station

Urine culture

Abdominal / Fundal exam to assess evidence of tenderness (infection)

Obtain fFN (if cervix hasn’t been digitally checked in 24 hrs and visually less than 3 cm dilated)

Sonogram if evidence of labor or other abnormality

Fetal Fibronectin

Fetal fibronectins are large molecular weight glycoproteins found in the plasma and extracellular matrix.

Identified in amniotic fluid, extracts of placental tissue, and malignant cell lines, and is recognized by the monoclonal antibody FDC-6.

Indicated for 22-34 weeks gestation.

Fetal Fibronectin

FFN is thought to be a "trophoblast glue" that promotes cellular adhesion at uterine-placental and decidual-fetal membrane interfaces. It is released into cervicovaginal secretions when the extracellular matrix of the chorionic/decidual interface is disrupted; this is the rationale for measurement of fFN as a predictor of PTD.

Preterm Contractions

Evidence of contractions, but not labor

IV/PO hydration

Benadryl 50mg IV/PO Q 6hr or

Terbutaline 0.25mg SQ Q 30 min

Prolonged observation

Reassurance

Preterm Labor

Evidence of Labor At what gestational age can the pediatrician

comfortably accept the neonate If < acceptable gestational age and pt remote from

delivery, tocolyze and arrange immediate transport

Start GBS prophylaxis

steroids Betamethasone or Dexamethasone if < 34 wks

If < acceptable gestational age and pt very near delivery, try to have NICU team receive the neonate and then transport to NICU

Preterm Labor Evidence of Labor

Tocolytics have not been shown to prolong pregnancy beyond a few days

MgSO4

Competes with Ca++ for entry into smooth muscle

β-adrenergic agents

Activation of adenyl cyclase, increased cAMP, decreased myosin light chain kinase activity

Ritodrine

Terbutaline

Prostaglandin synthetase inhibitors

Indomethacin

Ca++ channel blockers

Nifedipine

Preterm Labor

Evidence of Labor

Contraindications to tocolysis

Gestational age > 35-36 wks

Severely anomalous fetus

Intrauterine infection

Significant vaginal bleeding

Other obstetric conditions such as non-reassuring fetal status

Preterm Labor

Evidence of Labor

When in doubt, stabilize patient and transfer to center with a NICU.

Patient may arrest with advanced cervical dilation and it may be advisable that the patient not be further than 15-20 minutes away from a NICU.