Ultrasonographic Cervical Length and Risk of Hemorrhage in Pregnancies With Placenta Previa

Abstract

Placenta previa in pregnancy can lead to massive hemorrhage and premature birth and is a leading cause of maternal morbidity and mortality. A clear relationship between ultrasonographic cervical length and preterm birth has been demonstrated, especially among women with a previous preterm birth. In unselected populations, a cervical length cutoff of 30 mm has been associated with nearly a 4-fold relative risk for preterm birth. Only limited data are available on cervical length in women with placenta previa. This prospective study was designed to estimate the relationship between third-trimester cervical length and subsequent hemorrhage and preterm birth among women with placenta previa. Between 2007 and 2009, the investigators performed transvaginal cervical-length measurements on all singleton pregnancies with placenta previa identified by ultrasound at or beyond 24 weeks of gestation. Only women with confirmed placenta previa at delivery were included. Short cervical length was defined as 30 mm or less. All clinicians and patients were blinded as to cervical-length measurements. A total of 89 women with placenta previa were identified; of these, 68 (76%) had placenta previa at delivery, and 29 (43%) had cervical lengths 30 mm or less. There were no differences in the gestational age of the 2 groups at cervical length assessment (short cervix: 32 weeks vs. longer cervix: 33 weeks; P = 0.4). Among women with placenta previa, delivery for hemorrhage was more likely with a short cervix than a longer cervix (79% vs. 28%); women with a short cervix were also more likely to require delivery preterm (69% vs. 21%; P 30 mm were more likely to deliver at term without no bleeding or hospitalization (64% vs. 17%; P< 0.001). These findings show that women with placenta previa who have a third-trimester cervical length of 30 mm or less are at increased risk for hemorrhage, uterine contractions, and preterm birth compared to women who have a longer cervix.