Predicting which women are at highest risk for preterm delivery

While the Bishop score performs better than a cervical score in the mid-trimester as a predictor of spontaneous preterm delivery, by 26 to 29 weeks' gestation, the situation reverses, and a cervical score less than 1.5 better predicts spontaneous delivery by 35 weeks than a Bishop score of at least 5.

The findings come from a prospective cohort study involving almost 3,000 women with singleton pregnancies. The researchers determined that at 22 to 24 weeks' gestation, a Bishop score of at least 4 is the superior predictor, but by 26 weeks, a cervical score less than 1.5 has a sensitivity of 35.7% and a false-positive rate of 4.8%, which is superior to a Bishop score of at least 5 (P<.001).

The authors of the study caution that the findings may not be transferable to private practice because the population studied may have been at higher baseline risk for preterm delivery. The women were mostly of relatively poor socioeconomic status, and almost 16% had a history of spontaneous preterm delivery.