Second-trimester transvaginal ultrasound measurement of cervical length for prediction of preterm birth : a blinded prospective multicentre diagnostic accuracy study
Objective: To estimate the diagnostic performance of sonographic cervical length for the prediction of preterm birth (PTB). Design: Prospective observational multicentre study. Setting: Seven Swedish ultrasound centres. Sample: A cohort of 11 456 asymptomatic women with a singleton pregnancy. Methods: Cervical length was measured with transvaginal ultrasound at 18–20 weeks of gestation (C×1) and a