Serum relaxin and cervical length for prediction of spontaneous preterm birth in second‐trimester symptomatic women

ABSTRACT Objective To investigate whether serum relaxin level is associated with preterm birth in symptomatic women, either as a standalone test or in the context of a combined model of serum relaxin and cervical length (CL). Methods This was a case–control study of women with a singleton pregnancy who presented between 24 + 0 and 26 + 6 weeks' gestation with threatened preterm labor and intact membranes. CL, full blood count, C‐reactive protein level and maternal demographics were recorded at presentation, and blood samples were taken for relaxin measurement. Parameters were compared between women who delivered preterm (before 37 weeks) (n = 46) and those delivering at term (n = 66). Logistic regression with receiver–operating characteristics (ROC) curve analysis was used to assess significant predictors for birth before 37 and before 34 weeks. Results Women delivering before 37 weeks had higher mean serum relaxin levels and lower mean CL than those delivering at term (P 1010 pg/mL had 58% sensitivity for prediction of preterm birth in women with a CL > 15 mm, at a 10% FPR. Conclusions High serum relaxin level is associated with an increased risk of preterm birth in second‐trimester symptomatic women with intact membranes. A combination of serum relaxin and CL increases predictive accuracy for preterm birth. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.