Clinical and sonographic parameters at mid-trimester and the risk of cesarean delivery in low-risk nulliparas.

Background: To examine the potential clinical and sonographic parameters at mid-trimester that predict the risk of intrapartum cesarean delivery at term among low-risk nulliparas.

Methods: This prospective study recruited nulliparas with singleton low-risk pregnancies at 20.0-24.0 weeks. Sonographic measurement of the cervical length and fetal biometry was performed. The data collected at enrollment included maternal age, measured weight at first prenatal visit to the hospital, current weight, height, fetal biometric parameters, and cervical length. A multivariate analysis was conducted, with control for known intra- and postpartum confounding factors associated with cesarean delivery, including sex of the fetus.

Results: Based on multivariate analyses of 652 women, of all variables at mid-trimester, only maternal height was significantly associated with increased risk of cesarean delivery (61, 9.4%), whereas for intra- or postpartum variables, induction of labor, epidural analgesia, male gender, and nightshift delivery showed statistically significant association with the risk of cesarean delivery.

Conclusions: Maternal height and fetal gender, as measured at mid-trimester, are potential independent predictors for the risk of intrapartum cesarean delivery at term in low-risk nulliparas; however, sonographic measurements of the cervical length, fetal biometric ratio, maternal age, and current weight at mid-trimester were not predictive of cesarean delivery at term. © 2014 Wiley Periodicals, Inc. J Clin Ultrasound 43:235-242, 2015.