The risk of preterm delivery and pregnancy outcomes in women with asymptomatic short cervix: a retrospective cohort study

Objective: Routine cervical length measurement in asymptomatic pregnant women to prevent preterm birth has not been universally adopted due to poor predictive accuracy. The purpose of our study was to evaluate the risk of preterm delivery and pregnancy outcomes in women with asymptomatic short cervix and examine the implications of gestational age at presentation on these outcomes. Study design: This was a retrospective cohort study of women with singleton pregnancies who presented prior to or at 32 + 0 weeks with an asymptomatic short cervix (<= 25 mm) between April 2014 to March 2018 at a single tertiary maternity center. Women with cervical length <= 25 mm were grouped into four cohorts according to gestational age at presentation: Obstetric outcomes were compared between the cohorts and the general cohort of women delivering during the same period. Outcomes were compared using Mann-Whitney U, chi-square tests, and logistic regression. Survival analysis was carried out to compare the probability of delivery for each subgroup. Results: The rate of spontaneous preterm birth <37 weeks was highest in the cohort presenting at 25 + 0-27 + 6 weeks, and lowest in the first cohort presenting at <22 + 0 (60.0 versus 22.2%, p < .05). When compared with the general cohort, the rate of spontaneous preterm birth at <37-week gestation was significantly higher in the asymptomatic short cervix cohort (40.4 versus 8.7%, p < .001), with a 7.1-fold increase in the relative risk of spontaneous PTB. Conclusions: In asymptomatic women, cervical shortening showed significant increase in the risk of preterm birth. Our study findings suggest that routine cervical screening may be helpful in predicting risk of preterm birth even in women who are considered low-risk for preterm birth.