Cervical dilatation on presentation for preterm labor and subsequent preterm birth.

We sought to determine the risk of preterm (< 32 weeks) delivery as it relates to cervical dilatation at presentation of an initial preterm labor admission episode. We retrospectively reviewed the records of all patients presenting with preterm contractions at 22 to 32 weeks' gestation. Multiple regression was used to analyze the relationship between the interval from initial preterm labor admission episode to delivery and cervical dilatation at presentation. Logistic regression analysis was used to identify variables associated with preterm birth. Mean gestational age on admission for preterm labor episode was 28.1 +/- 2.9 weeks. With a cervical dilatation of 0 to 1 cm, 6% of the women delivered within 48 hours, 20% delivered at < 32 weeks, and 38% delivered at < 35 weeks. With cervical dilatation of 6 to 10 cm, 89% delivered in < 24 hours, 11% between 24 and 48 hours, 94% delivered at < 32 weeks, and 100% delivered at < 35 weeks. Time from admission for initial preterm labor episode to delivery was inversely associated with cervical dilatation. Variables associated with preterm birth at < 32 weeks' gestation were cervical dilatation ( P < 0.0001), gestational age ( P < 0.0001), and effacement ( P < 0.0001) at presentation. In women who experience preterm contractions, cervical dilatation on admission is inversely related to interval to delivery. However, women with cervical dilatation of 0 to 1 cm are still at significant risk for preterm delivery: 19/94 (20%) at < 32 weeks' gestation and 40/104 (38%) at < 35 weeks' gestation.