Transactions of the Twentieth Annual Meeting of the Society For Maternal-Fetal Medicine—Continued
Use of cervical ultrasonography in prediction of spontaneous preterm birth in twin gestations

Presented at the Twentieth Annual Meeting of the Society for Maternal-Fetal Medicine, Miami Beach, Florida, January 31–February 5, 2000.
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Abstract

Objective: This study was undertaken to compare various ultrasonographic cervical parameters with respect to ability to predict spontaneous preterm birth in twin gestations. Study Design: This prospective study involved 131 women carrying twins who were longitudinally evaluated on 524 occasions between 15 and 28 weeks’ gestation with transvaginal cervical ultrasonography and transfundal pressure. The following cervical parameters were obtained: funnel width and length, cervical length, percentage of funneling, and cervical index. Receiver operating characteristic curve analysis was used to determine the ultrasonographic cervical parameter evaluated at 15 to 20 weeks’ gestation, 21 to 24 weeks’ gestation, and 25 to 28 weeks’ gestation that were best for prediction of spontaneous preterm birth at <28 weeks’ gestation, <30 weeks’ gestation, <32 weeks’ gestation, and <34 weeks’ gestation. Results: The median gestational age at delivery was 36 weeks’ gestation (range, 21-41 weeks’ gestation). Receiver operating characteristic curve analysis indicted that a cervical length of ≤2.0 cm, regardless of gestational age category at cervical measurement, was at least as good as other ultrasonographic cervical parameters at predicting spontaneous preterm birth. Between 15 and 20 weeks’ gestation a cervical length cutoff value of ≤2.0 cm had specificities of 97%, 98%, 99%, and 100% and negative predictive values of 99%, 98%, 95%, and 89% for delivery at <28, <30, <32, and <34 weeks’ gestation, respectively. The positive predictive values for delivery at <32 and <34 weeks’ gestation were 80% and 100%, respectively. Between 21 and 24 weeks’ gestation a cervical length of ≤2.0 cm had specificities of 84%, 84%, 85%, and 86% and negative predictive values of 99%, 99%, 94%, and 87% for delivery at <28, <30, <32, and <34 weeks’ gestation, respectively. Between 25 and 28 weeks’ gestation cervical length had excellent negative predictive values of 99%, 98%, 95%, and 93% for delivery at <28, <30, <32, and <34 weeks’ gestation, respectively. Conclusions: In twin gestations a cervical length of ≤2.0 cm measured between 15 and 28 weeks’ gestation was at least as good as other ultrasonographic cervical parameters at predicting spontaneous preterm birth. The high specificities indicate that cervical length was better at predicting the absence than the presence of various degrees of spontaneous prematurity. (Am J Obstet Gynecol 2000;183:1103-7.)

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Material and methods

This prospective study involved 131 women with twin gestations who were longitudinally evaluated on 524 occasions with serial transvaginal ultrasonography and transfundal pressure between 15 and 28 weeks’ gestation. The study was undertaken in the antenatal testing unit at Saint Peter’s University Hospital, New Brunswick, NJ, between September 1993 and June 1999. At each examination the funnel width, funnel length, cervical length, percentage of funneling (considered to be Funnel length/[Funnel

Results

Table I depicts the maternal demographic data and obstetric history. Table II summarizes the pregnancy outcomes.

. Maternal demographic data and obstetric history (N = 131)

Maternal age (y, median and range)33.2 (18-46)
Race (No.)
 White87 (66.4%)
 Black21 (16.0%)
 Hispanic5 (3.8%)
 Other17 (13.1%)
Parity (No.)
 Nulliparous73 (56%)
 Primiparous33 (25%)
 Multiparous25 (19%)
History of spontaneous preterm delivery at 24-37 wk (No.)11 (8.4%)
History of second-trimester loss (No.)5 (3.8%)
Previous cerclage (No.)2 (1.5%)

Comment

Other studies have assessed cervical ultrasonography as a screening test for spontaneous preterm birth in twin gestations. Imseis et al3 measured cervical length between 24 and 26 weeks’ gestation in 85 twin gestations. Because many of their patients required some form of intervention, they focused on identification of a subset of twin gestations at low risk for delivery at <34 weeks’ gestation. They established a cervical length cutoff value of >3.5 cm for prediction of delivery at ≥34 weeks’

Acknowledgements

We gratefully acknowledge Cande V. Ananth, PhD, MPH, for the expertise in research design and statistical support provided.

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Reprint requests: Edwin R. Guzman, MD, Associate Professor of Obstetrics and Gynecology, Director of Antenatal Testing Unit, Saint Peter’s University Hospital, 254 Easton Ave, MOB 4th Floor, New Brunswick, NJ 08903-0591.

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