First-trimester screening for spontaneous preterm delivery with maternal characteristics and cervical length.

OBJECTIVE It was the aim of this study to examine the potential value of cervical length at 11-13 weeks' gestation in the prediction of spontaneous preterm delivery. METHODS This was a screening study for spontaneous preterm delivery in singleton pregnancies from cervical length measured by transvaginal ultrasound at 11-13 weeks' gestation. The performance of screening for preterm delivery by cervical length alone and with maternal characteristics was estimated. RESULTS In the 9,974 pregnancies included in the study, spontaneous delivery before 34 weeks occurred in 104 (1.0%) cases. Multivariate regression analysis in the term delivery group demonstrated that for the log(10) cervical length, significant independent contributions were provided by fetal crown-rump length, maternal height, age, racial origin and parity. The median cervical length multiple of the median (MoM), corrected for maternal characteristics, was significantly lower in the preterm (0.892 MoM, 95% CI 0.829-0.945) than in the term delivery group (0.994 MoM, 95% CI 0.919-1.082; p < 0.0001). In screening by a combination of maternal characteristics and cervical length, the estimated detection rate of preterm delivery was 54.8% (95% CI 44.7-64.6), at a false-positive rate of 10%. CONCLUSIONS Effective first-trimester screening for spontaneous early preterm delivery can be provided by a combination of maternal characteristics and cervical length.