Advertisement

39: Cervical funneling: effect on gestational length and ultrasound-indicated cerclage in high-risk women

      Objective

      To assess the relationship between the type of cervical funneling and birth gestational age (GA) in women with prior spontaneous preterm birth (SPTB) and cervical length (CL) < 25 mm enrolled in a randomized intervention trial of ultrasound-indicated cerclage.

      Study Design

      This is a planned secondary analysis of the NICHD-sponsored cerclage trial. Women with prior SPTB at 17 – 33 6/7 weeks underwent serial vaginal scans between 16 and 22 6/7 weeks. 301 women whose CL was < 25 mm were randomized to receive cerclage or no cerclage. At the qualifying scan for randomization, the presence and type of funnel (U or V-shaped) were recorded.

      Results

      147 of 301 (49%) had a funnel: 99 were V-shaped (V-F) and 48 were U-shaped (U-F). In univariate analyses, the presence of U-F, but not V-F, was associated with an increased risk of preterm birth < 24 weeks (p= 0.0092), < 28 weeks (p=0.0002), < 35 weeks (p=0.0005), and < 37 weeks (p=0.002). In a multivariable regression model of GA as the dependent variable, U-F (but not V-F) remained significant (p=0.003) after controlling for baseline CL and cerclage group, demonstrating a mean 3 week earlier birth. We also considered the possibility of an interaction between U-F and cerclage. The interaction term (p=0.06) suggested that women with U-F have a disproportionate benefit from cerclage: women with U-F were delivered a mean 4.9 weeks later in gestation with cerclage than without cerclage.

      Conclusion

      The finding of a U-F, but not a V-F, in women with shortened midtrimester CL is associated with a earlier birth GA. The pathophysiologic mechanisms of a U-F appear to be more amenable to cerclage therapy in women with prior SPTB and shortened CL < 25 mm.