Predictive value of transvaginal cervical length in triplet pregnancies for spontaneous preterm delivery at ≤ 32 weeks

Abstract

Objective: To establish whether cervical length is a predictor of spontaneous preterm delivery at ≤ 32 weeks in triplet pregnancies.Methods: This was a case-control study of all tripletpregnancies followed with more than three sonographic assessments of cervical length at 4-week intervals from 1995 to 2000. Cervical length in women delivered spontaneously at ≤ 32 weeks (cases) wascompared with that of the remaining women (controls). Statistical analysis included Fisher's exact test, χ2 test, one-way analysis of variance, logistic regression and receiver operatingcharacteristic (ROC) curve to determine optimal cervical length thresholds for spontaneous preterm delivery at ≤ 32 weeks.Results: Of the 58 women included in the study, 17 (29%) deliveredspontaneously at ≤ 32 weeks. The preterm delivery group had similar demographic and obstetric variables, but a higher rate of cerclage placement (65% vs 17%, p < 0.001) than controls. Mean± standard deviation cervical length was significantly shorter among cases than controls at 16-20.0 weeks (3.0 ± 1.2 vs. 3.9 ± 0.8 cm, p = 0.01), but not at 20.1-24.0 weeks (3.5± 1.1 vs. 3.8 ± 1.0 cm, p = 0.76). Logistic regression analysis determined that cervical length at 16-20 weeks had an odds ratio of 0.43 (95% CI = 0.23, 0.80) for the prediction ofspontaneous preterm delivery at ≤ 32 weeks. ROC curve analysis identified a cervical length of ≤ 2.6 cm as the optimal threshold for the prediction of spontaneous preterm delivery at ≤ 32 weeks(sensitivity 41%, specificity 92%).Conclusions: In a population of triplet gestations with a 29% rate of preterm delivery, cervical length at 16-20.0 weeks, but not at 20.1-24.0 weeks, was inverselycorrelated with the probability of preterm delivery at ≤ 32 weeks.