Cervical Length and Delivery Outcomes inPatients with Prophylactic Cervical CerclageJoseph G. Ouzounian, M.D.,1 Lisa M. Korst, M.D., Ph.D.,1 and Richard H. Lee, M.D.1

ABSTRACT

We sought to determine the relationship between cervical length and deliveryoutcome in patients who received prophylactic cervical cerclage. We performed a retro-spective cohort study of patients with singleton gestations who underwent cerclage duringcalendar years 1999 to 2008. A total of 78 patients were included in the study. Multipleclinical characteristics and their relationships to delivery outcome were analyzed usingmultivariable logistic regression analysis. Cervical length at the time of surgery and historyof one or more prior second-trimester losses were strongly associated with delivery at orafter 32 weeks gestation (p¼ 0.005 and p¼ 0.01, respectively). In fact, a cervical lengthgreater than 2 cm at the time of surgery was associated with delivery at 32 weeks or greater(odds ratio 5.74, 95% confidence interval 1.78 to 18.5; p¼ 0.003). Cervical length wasassociated with the delivery outcome of patients with prophylactic cerclage and may behelpful in selection of surgical candidates.

KEYWORDS: Cerclage, cervical length, preterm delivery

Cervical insufficiency has been defined histor-ically as painless dilation of the cervix resulting inmidtrimester pregnancy loss or rupture of membranes.Because cervical insufficiency is implicated in 10 to 25%of second-trimester pregnancy losses,1,2 considerableinterest has been generated over the years in surgicalprocedures aimed at correcting the anatomic defect.Dr. Shirodkar first reported his surgical technique forcervical cerclage in 1955.3 A simplified procedure waslater described by McDonald in 19574 with modificationsby Marshall and Evans in 1967.5 Cervical cerclageremains a standard technique for the treatment of cervicalinsufficiency. In fact, some reports have estimated thatup to 2% of pregnancies result in cerclage procedures.6

In patients with an appropriate clinical history,cerclage is offered prophylactically and placed early inthe second trimester. In other cases, patients with or

without a significant history present later in pregnancywith either cervical shortening on ultrasound or cervicaldilatation on physical exam and undergo rescue cerclageplacement. Although several reports have analyzed out-comes in patients with cerclage,7–10 the relationship ofoutcome to cervical length at the time of the procedureremains unclear. As such, the purpose of the presentstudy was to investigate the relationship between cervicallength in cerclage patients and its relationship to preg-nancy outcome.

MATERIALS AND METHODSWe performed a retrospective cohort analysis of allpatients undergoing cervical cerclage from 1999 to 2008at the Kaiser Permanente Baldwin Park Medical Center.Patient information was abstracted from computerized

1Division of Maternal-Fetal Medicine, Department of Obstetrics andGynecology, Keck School of Medicine, University of SouthernCalifornia, Los Angeles, California.

Address for correspondence and reprint requests: Joseph G.Ouzounian, M.D., LAC+USC Medical Center, Department ofObstetrics and Gynecology, 1200 N. State Street, IRD Room 220,Los Angeles, CA 90033 (e-mail: jouzouni@usc.edu).

Am J Perinatol 2011;28:273–276. Copyright # 2011 by ThiemeMedical Publishers, Inc., 333 Seventh Avenue, New York, NY10001, USA. Tel: +1(212) 584-4662.

Received: April 12, 2010. Accepted after revision: October 19,2010. Published online: December 6, 2010.DOI: http://dx.doi.org/10.1055/s-0030-1270110.ISSN 0735-1631.

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medical record databases and augmented with chart re-view where appropriate. This study was approved by theInstitutional Review Board and complied with all perti-nent human subject stipulations contained therein.

The standardized prenatal program at this med-ical center stipulates that all women have their obstetrichistory reviewed and also have an ultrasound assessmentof fetal viability and gestational age at their initialprenatal visit. Patients with an appropriate clinical his-tory are then referred for evaluation by a Maternal-FetalMedicine (MFM) attending physician. Patients with agestational age less than 16 weeks with a history of priorsecond-trimester loss, prior cerclage, abnormal cervix,prior cervical or uterine surgery, or cervical shortening,dilation, and or funneling on transvaginal (TV) ultra-sound were considered cerclage candidates. Patients withmultiple gestations, preterm premature rupture of mem-branes, or fetal anomalies were excluded. Preoperatively,the TV ultrasound was repeated to corroborate fetalviability as well as record cervical length. After detailedinformed consent, these patients had a McDonald cer-vical cerclage in the operating room under regionalanesthesia using standard technique.5 All procedureswere performed by the same attending MFM physician.The procedure was performed with either 5 mmMersilene1 (Ethicon, Inc., Cincinnati, OH) or No. 1Prolene1 (Ethicon, Inc., Cincinnati, OH) suture. Allpatients who consented to the procedure and had surgerywere included in the study. Patients with protrudingmembranes were not excluded from analysis.

Maintenance of pregnancy to 32 weeks’ gestationwas chosen a statistical end point, although other thresh-olds for survival were also analyzed as long-term survivalof infants born at or beyond 26 weeks’ gestation has beenreported to be over 80%.11 Operative complications weredefined as blood loss during surgery > 25 mL, post-operative infection, or cervical laceration.

For comparison of categorical variables, x2 testswith Yates correction or Fisher exact tests were used.Continuous variables were analyzed with Wilcoxonrank-sum tests. Means are expressed� the standarddeviation, and relative risks and adjusted odds ratios(OR) are expressed with 95% confidence intervals (CI).All analyses were two-sided, with a p value <0.05considered statistically significant. Multivariable linearand logistic regression models were used to explore therelationship between cervical length and other perinatalcharacteristics and gestational age at delivery (SASResearch Institute, Cary, NC).

RESULTSA total of 78 patients underwent cervical cerclage.Characteristics of the patients are summarized inTable 1. The mean cervical length at the time of surgerywas 1.4� 0.8 cm (range 0.3 to 3.4 cm).

Table 2 summarizes patient outcome. Overall, 61(78.2%) patients delivered at � 32 weeks’ gestation and17 (21.8%) patients did not. A cervical length greaterthan 2 cm at the time of surgery was associated withdelivery after 32 weeks (OR 5.74, 95% CI 1.78 to 18.5;p¼ 0.003). When analyzed with a multivariable logisticregression model with variables including maternal age,gestational age, cervical length > 2 cm, uterine anomalyor prior cervical/uterine surgery, prior cerclage, suturetype, and prior second-trimester loss, all variables re-mained unassociated with delivery after 32 weeks exceptcervical length greater than 2 cm at the time of surgery(as noted above) and history of one or more priorsecond-trimester loss (OR 4.54, 95% CI 1.06 to 42.8;p¼ 0.01). This relationship of cervical length and gesta-tional age at delivery remained statistically significantwhen 26-, 28-, and 34-week delivery thresholds wereanalyzed separately (p¼ 0.009, p¼ 003, and p¼ 0.006,respectively).

A linear regression model using the same variablesnoted above demonstrated that gestational age at deliv-ery decreased by 4.6 weeks for a history of second-trimester loss and increased by 3.5 weeks for each1-cm increase in preoperative cervical length(p¼ 0.0005 and p<0.001, respectively; R2¼ 0.29).

DISCUSSIONApproximately 1% of patients with risk factors forpreterm birth receive a cervical cerclage.12,13 In thepresent study, we have demonstrated that treatment ofcervical insufficiency with cervical cerclage can prolongpregnancy in a significant number of patients. Althoughthe relationship between preoperative cervical lengthand outcome has been reported previously,14–16 there is

Table 1 Characteristics of Study Patients

n 78

Age (y) 30.7�4.8

GA at surgery (wk) 13.6�1.1

5-min Apgar <7 8 (10.5%)

Delivery � 32 wk 61 (78.2%)

Birth weight (g) 2788�1123

GA at delivery (wk) 34.9�6.3

Operative complications 0

Single second-trimester loss 53 (69.7%)

Second-trimester loss >1 22 (28.2%)

Prior cervical surgery 8 (10.3%)

Short cervix� funneling 6 (7.7%)

Mersilene suture 72 (92.3%)

Prolene suture 4 (5.1%)

Cervical length >2 cm 59 (75.6%)

Chorioamnionitis 4 (5.1%)

Cesarean section 28 (36.8%)

GA, gestational age.

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a paucity of data that estimate the effects of cervicallength on delivery outcome. Our results demonstratethat cervical length at the time of surgery is associatedwith delivery outcome and may be helpful in counselingpatients contemplating surgery. Although prior preg-nancy history was also statistically associated with out-come, this is less useful clinically because typicallypatients present for subspecialty consultation based onthis historical finding.

When compared with expectant management,previous studies of cervical cerclage have not demon-strated consistent benefit with regards to outcome.14,17–19

The overall effectiveness of prophylactic cerclage inpreventing preterm delivery has also been questioned.20

Nevertheless, in patients with compelling clinical histor-ies, it is common in modern obstetric practice as partof informed consent to discuss cerclage as at least onepotential therapeutic option. As such, informationregarding objective parameters such as preoperativecervical length in a quantitative format as outlined inthe present study can help mitigate the lack of conclusiveevidence from randomized clinical trials. Moreover,patient heterogeneity and physician expertise in per-forming the procedure are also issues for appropriateconsideration when contemplating surgery and counsel-ing patients.

A commonly reported complication related to thecerclage procedure is infection, with rates as high as 8%reported in some series.21 In the present study, weobserved low infection rates (defined as clinical cho-rioamnionitis) and no operative complications (Table 1).We recognize, however, that the study may lack suffi-cient power to detect these or other complicationssufficiently.

We recognize the limitations of the present study,including the small sample size, potential selectionbias, and wide confidence intervals. Nevertheless, thestrengths of the study are that the patients described arefrom a single institution and a single surgeon, reducing

the potential for technique-related and diagnosis-relatedheterogeneity. Moreover, the robust quantitative rela-tionship of cervical length and delivery outcome de-scribed may provide a useful guide for clinical decisionmaking and patient counseling.

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Table 2 Characteristics of Patients with Prophylactic Cerclage

Delivery <32 wk Delivery � 32 wk p

n (%) 17 (21.8%) 61 (78.2%)

Age (y) 29.9� 4.6 30.9�4.9 0.60

GA at surgery (wk) 13.9� 1.8 13.6�0.8 0.74

Mersilene suture 15 (88.2%) 57 (93.4%) 0.60

Prolene suture 1 (5.9%) 4 (6.6%) 0.61

Birth weight (g) 877�574 3338�400 <0.0001

Cervical length > 2 cm 8 (47.1%) 51 (83.6%) 0.0054

Single second-trimester loss 17 (100%) 38 (62.3%) 0.011

Multiple second-trimester losses 11 (64.7%) 11 (18.0%) <0.001

Prior cerclage 8 (47.1%) 16 (26.2%) 0.18

Cervical or uterine surgery 0 8 (13.1%) 0.26

GA, gestational age.

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