Cervical funneling is more predictive of preterm birth than cervical length alone in nulliparous women

Abstract

Universal mid-trimester cervical length (CL) screening is a well-accepted practice for detection of women at risk of spontaneous preterm birth (sPTB). In those identified with a short cervix, progesterone supplementation is recommended. However, current guidelines do not consider a short cervix an indication for cerclage without a history of sPTB as it has poor sensitivity for this outcome. It is currently unclear if other sonographic features such as cervical funneling can identify a higher sPTB risk in a population without prior sPTB. This was a secondary analysis of the nuMom2b study, which enrolled a large prospective observational cohort of pregnant nulliparous women. Patients were stratified based on CL < 25mm or ≥25mm and presence or absence of funneling at the time of cervical length evaluation between 16-22 weeks’ gestation. Logistic regression was used to calculate adjusted odds ratios (aOR) and 95% confidence intervals (CI) for sPTB adjusting for confounders. A Kaplan-Meier survival analysis was performed between groups and gestational age at delivery. 7,648 nulliparous women were included in the analysis. There were 169 (2.2%) women identified with a short CL < 25 mm and 52 (0.7%) with funneling. While a short CL had a higher risk of PTB (Table 1), a short CL was detected in only 24 (7.1%) of women who ultimately had a sPTB. The presence of a funnel was independently associated with higher odds of sPTB (OR 3.4, CI 1.9-8.1) when compared to CL < 25mm (OR 2.7, CI 1.7-4.4). On survival analysis, a short CL with funneling showed the lowest mean gestational age at delivery (Figure 2, p< .001). In a nulliparous population without prior sPTB, transvaginal cervical length alone is a poor predictor of preterm delivery, but presence of funneling significantly increases risk. This may identify a population of women who would benefit from cerclage.View Large Image Figure ViewerDownload Hi-res image Download (PPT)