Effect of second‐trimester sonographic cervical length on the risk of spontaneous preterm delivery in different risk groups: A prospective observational multicenter study

Abstract Introduction The aim of the study is to compare effect cervical length measured with transvaginal ultrasound in second trimester on risk spontaneous preterm delivery (PTD) between different groups asymptomatic women a singleton pregnancy. Material and methods This pre‐planned exploratory analysis CERVIX study, prospective blinded multicenter diagnostic accuracy study. Asymptomatic pregnancy were consecutively recruited at their second‐trimester routine examination seven Swedish centers. Cervical was 18–20 weeks (Cx1; n = 11 072) 21–23 (Cx2, optional; 6288). PTD its discriminative ability compared with: (i) previous PTD, late miscarriage or conization (high‐risk group; 1045); (ii) nulliparae without factors ( 5173); (iii) parae 4740). Women indicated excluded 114). Main outcome measures were: expressed as odds ratio per 5‐mm decrease interaction using logistic regression test whether differed groups, area under receiver operating characteristic curve (AUC), sensitivity, specificity, number needed screen detect one PTD. Results Cx2 <33 similar all (odds ratios 2.26–2.58, p value 0.91). superior that Cx1 (AUC 0.69–0.76). ≤25 mm identified 57% deliveries high‐risk group 161. for 1018 843. Conclusions high‐ low‐risk pregnancies. differences should be considered before implementing screening program.