Cervical Length and Risk of Hemorrhage in Pregnancies With Placenta Previa

To find out the relationship between ultrasonographic cervical length and risk of antepartum hemorrhage, preterm delivery and emergency caesarean section in pregnancies with placenta previa.

We performed transvaginal cervical-length measurements on all singleton gestations with placenta previa admitted in our hospital at or beyond 24 weeks of gestation over a span of one year. A complete follow-up of pregnancy was obtained in all cases till delivery and a retrospective chart review was then performed for these cases to investigate the relationship between cervical length and maternal and neonatal outcome. Results: Overall 70 patients comprised the study, in whom placenta previa persisted till delivery. Cervical length measurement was <30 mm in 27 (38.6%) cases while it was >30 mm in 43 (61.4%) cases. Cervical length ranged from 20 to 50 mm with a mean of 35.6±0.90 mm. Majority of subjects (51.9%) in whom measurements were done between 28–32 weeks had cervical length <30 mm, however, all the subjects (100%) in whom measurements were done after 32 weeks of gestational age had cervical length >30 mm.

The association between gestational age and cervical length was statistically significant (p<0.001). Forty five patients (64%) presented with antepartum bleeding. Among the women with shorter cervical length, 25 (92%) had antepartum bleeding (p<0.001) and 22(81%) had emergency caesarean section (p<0.001). In comparison, those with longer cervical length, 20 (46%) had bleeding episode and 14 (32%) had emergency caesarean section. Likewise, of the 27 subjects who had cervical length <30 mm, 25 (92%) had preterm delivery and two (8%) had term delivery. Significant association was present between short cervical length and preterm delivery (p=0.029). Also cervical length <30 mm, presence of antepartum hemorrhage and first episode of hemorrhage <32 weeks were significantly associated with stillbirth/NICU admission (p<0.05).

In pregnancies with placenta previa, a third-trimester transvaginal sonographic cervical length of 30 mm or less is associated with increased risk for hemorrhage, emergency caesarean section and preterm birth.