Clinical significance of early (< 20 weeks) vs. late (20-24 weeks) detection of sonographic short cervix in asymptomatic women in the mid-trimester

Objective: The aim of this study was to determine whether the risk of early spontaneous preterm delivery (PTD) in asymptomatic women with a sonographic cervical length of ≤ 15 mm in the mid-trimester changes as a function of gestational age at diagnosis.

Methods: This cohort study included 109 asymptomatic patients with a sonographic cervical length of ≤ 15 mm diagnosed at 14-24 weeks of gestation. Women with a multifetal gestation, cerclage and a cervical dilatation of > 2 cm were excluded. The study population was stratified by gestational age at diagnosis (< 20 weeks vs. 20-24 weeks) and by cervical length (≤ 10 mm vs. 11-15 mm). The primary outcome variables were PTD at < 28 and < 32 weeks of gestation and the diagnosis-to-delivery interval.

Results: The median gestational age at diagnosis of a short cervix before 20 weeks and at 20-24 weeks was 18.9 and 22.7 weeks, respectively. Women diagnosed before 20 weeks had a higher rate of PTD at < 28 weeks (76.9% vs. 30.9%; P < 0.001) and at < 32 weeks (80.8% vs. 48.1%; P = 0.004), and a shorter median diagnosis-to-delivery interval (21 vs. 61.5 days, P = 0.003) than those diagnosed at 20-24 weeks. The rate of amniotic fluid sludge was higher among patients diagnosed with a short cervix at < 20 weeks of gestation than in those in whom it was diagnosed between 20 and 24 weeks (92.3% vs. 48.2%; P < 0.001).

Conclusions: Asymptomatic women with a sonographic cervical length of ≤ 15 mm diagnosed before 20 weeks of gestation have a dramatic and significantly higher risk of early preterm delivery than women diagnosed at 20-24 weeks. These findings can be helpful to physicians in counseling these patients, and may suggest different mechanisms of disease leading to a sonographic short cervix before or after 20 weeks of gestation.