Implementation of universal screening for preterm delivery by mid-trimester cervical-length measurement

Objective To assess the feasibility and results of introducing a policy of universal screening for preterm delivery (PTD) by mid-trimester cervical-length (CL) measurement. Methods In this retrospective cross-sectional study of singleton pregnancies, transvaginal sonography for CL measurement was performed at 20-24 weeks of gestation. Vaginal progesterone therapy was offered to women with CL <= 15 mm. The incidence of spontaneous PTD (sPTD) according to CL and the distribution of CL measurements were assessed. Rate of PTD before implementation of screening was compared with that after. Results A total of 10 506 singleton pregnancies were assessed. The decline rate was 1.32%. sPTD < 32 weeks, < 34 weeks and< 37 weeks occurred in 0.51%, 0.82% and 3.90% of pregnancies, respectively. CL measurement was best described by a mixture model distribution comprising a 'short' and a 'long' component. The percentage of the two components varied between subgroups of PTD, with the short component being greater the earlier the birth. CL, history of miscarriage, smoking status and prior PTD were independent predictors in the construction of a model predictive of PTD< 34 weeks (area under the curve = 0.74, P < 0.001). The rate of sPTD < 34 weeks in women with CL= 15mm receiving progesterone treatment was 20.4%. In the progesterone-treated group, a plateau was observed in the increase in risk for PTD for CL 9-13 mm, whereas below 9mm the risk increased exponentially. Following the introduction of mid-trimester CL measurement, there was a trend for reduction in the rate of any PTD< 34 weeks of about 20% in comparison with the prescreening period (odds ratio= 0.81; 95% CI, 0.59-1.13). Conclusions Universal screening for PTD by transvaginal sonographic measurement of CL at 20-24weeks is feasible and well accepted by pregnant women. This policy identifies a very high-risk group that may benefit from intervention. Copyright (c) 2018 ISUOG. Published by John Wiley & Sons Ltd.