Does the presence of a funnel increase the risk of adverse perinatal outcome in a patient with a short cervix?

Objective This study was undertaken to determine whether the presence of a dilated internal os (funneling or beaking) alters the outcome of patients with a short cervix documented by transvaginal ultrasound in the second trimester. Study design Between January 1998 and May 2004, all singleton pregnancies with a short cervix (≤2.5 cm) and no funnel between 16 and 24 weeksʹ gestational age were identified by query and review of the Lehigh Valley Perinatal Ultrasound Database. These no funnel patients were compared with patients with a short cervix and funnel matched in accordance with cervical length and risk factors. Multiple variables of perinatal outcome were identified and compared between the Funnel and No Funnel groups. Correlations between cervical measurements and gestational age at birth were analyzed. Results Of the 279 patients with a short cervix identified, 82 were singleton with a T-shaped cervix and no funnel and 82 patients matched with a typical Y-shaped funnel. There was no difference between groups with respect to maternal demographics, previous preterm birth (28.1% No Funnel group vs 36.5% Funnel group, P = .3), prior cervical surgery (24.3% vs 22.0%, P = .8), gestational age at entry (20.5 ± 2.1 vs 21.1 ± 2.4 weeks, P = .1), and cervical length (1.9 ± 0.4 vs 1.8 ± 0.5 cm, P = .1). The No Funnel group had significantly less readmissions for preterm labor (43.2% vs 67.1%, P = .004), chorioamnionitis (2.4% vs 23.2%, P = .0002), abruption (1.2% vs 13.4%, P = .007), preterm rupture of membranes (6.1% vs 23.4%, P = .002), and cerclage placement (23.2% vs 43%, P = .008). The neonates in the no funnel group delivered later (36.2% ± 4.6 vs 33.8 ± 5.4 weeks, P = .003), and had less morbidity and mortality (17.1% vs 37.8%, P = .02) compared with the Funnel group. The width and depth of the funnel did not correlate with perinatal outcome. Cervical length (R2 = 0.07, P = .02) and cervical funneling as a categorical variable (r = 0.3, P = .0002) did correlate with earlier delivery. Conclusion The disruption of the internal os, as documented by funneling, is a significant risk factor for adverse perinatal outcome (ie, preterm labor, chorioamnionitis, abruption, rupture of the membranes, and serious neonatal morbidity and mortality). Cervical funneling is best measured as a categorical variable (present or absent).