499 Midtrimester cervical length for the prediction of preterm birth: a new definition of short cervix?

Abstract

To estimate the optimal midtrimester cervical for the prediction of spontaneous preterm birth in asymptomatic pregnant women with singleton pregnancy. Design: A prospective observational cohort study of women undergoing midtrimester ultrasound between April 2018 and December 2019. Setting: Open, population-based study. Participants: Asymptomatic pregnant women with singleton pregnancy between 19 0/7 and 21 6/7 weeks of gestation. Exposures: All participants underwent cervical length measurement by transabdominal and/or transvaginal ultrasound. All cervical length ≤30mm were confirmed by transvaginal ultrasound. Main outcomes and measures: Spontaneous preterm birth before 35 and before 37 weeks. Receiver operating characteristics curve analyses were performed to assess the predictive ability and to determine the optimal cervical length cut-offs. Our secondary outcome was preterm birth. Of 3449 participants, 28 (0.8%) and 99 (2.9%) had spontaneous preterm birth before 35 and 37 weeks, respectively, and 245 (7.1%) had preterm birth. Our ROC curve analyses suggest that a cut-off of 30mm was the optimal cervical to predict spontaneous preterm birth before 35 weeks (sensitivity: 43%; specificity: 97%) and 37 weeks (sensitivity: 21%; specificity: 97%). While a cervical length less than 25 mm was an important risk factor for spontaneous preterm birth (relative risk of 31.1; 95% confidence interval of 13.4 to 73.4), women with a cervical length between 25 and 29 mm remains also at very high risk for spontaneous preterm birth (relative risk of 11.5 with 95% confidence interval of 3.8 to 34.7). A midtrimester cervical length below 30mm (instead of 25 mm) should be used to identify women at high-risk of spontaneous preterm birth.View Large Image Figure ViewerDownload Hi-res image Download (PPT)