Can Progesterone Prevent Preterm Birth in At-Risk Singleton Pregnancies?

Preterm birth is the leading cause of neonatal mortality and morbidity worldwide, and previous findings have suggested that administration of progesterone reduces the likelihood of preterm birth. To identify a population at risk for preterm delivery, investigators assessed cervical length in consenting women with singleton or twin pregnancies scheduled for routine ultrasonography at 20 to 25 weeks’ gestation. Women with cervical length ≤15 mm were asked to participate in a randomized international trial of vaginal progesterone. Participants (median age, 29; 56% nulliparous; 55% black) inserted micronized progesterone (200 mg) or placebo capsules vaginally at bedtime from 24 through nearly 34 weeks’ gestation; 226 had singleton pregnancies, …