Cervical funneling or intra‐amniotic debris and preterm birth in nulliparous women with midtrimester cervical length less than 30 mm

Objective To evaluate whether the presence of cervical funneling or intra-amniotic debris identified in the second trimester is associated with higher rates of preterm birth (PTB) in asymptomatic nulliparous women with a midtrimester cervical length (CL) less than 30 mm (i.e., less than the 10th percentile). Methods A secondary cohort analysis of a multicenter trial of women between 16 and 22 weeks with a singleton gestation and a CL less than 30 mm by transvaginal ultrasound randomized to either 17-alpha hydroxyprogesterone caproate or placebo. Sonographers were centrally certified in CL measurement, as well as identification of intra-amniotic debris and cervical funneling. Univariable and multivariable analyses were performed. Results Of the 657 randomized women, 112 (17%) had only a cervical funnel, 33 (5%) had only intra-amniotic debris, and 45 (7%) had both on the second trimester ultrasound. Women with either of these findings had a shorter CL (19.5 vs. 25.6 mm, p<0.001) than those without these findings. PTB prior to 37 weeks was more likely for women with a funnel (37% vs. 21%; OR 2.2, 95% CI 1.5-3.3) or debris (35% vs. 23%, OR 1.7, 95% CI 1.1-2.9). Results were similar for PTB before 34 and 32 weeks’ of gestation. After multivariable adjustment that included CL, PTB prior to 34 or 32 weeks continued to be associated with the presence of debris (aOR 1.85, 95% CI 1.00-3.44; aOR 2.78, 95% CI 1.42-5.45, respectively), but not cervical funneling (aOR 1.17, 95% CI 0.63-2.17; aOR 1.45, 95% CI 0.71-2.96, respectively). Conclusions Among asymptomatic nulliparous women with a midtrimester cervical length less than 30 mm, the presence of intra-amniotic debris, but not a cervical funnel, is associated with increased risk of PTB < 34 weeks of gestation independently of the CL.