Preterm birth prevention.

Preterm birth (PTB), which occurs in about 12% of pregnancies worldwide, is the main cause of neonatal morbidity and mortality. Symptomatic treatment of pregnancies presenting in preterm labor with corticosteroids and antibiotics has improved neonatal outcomes but has not reduced the incidence of PTB. Evidence suggests that the rate of PTB may be reduced by the prophylactic use of progesterone in women with a previous history of preterm delivery and in those with a short cervical length identified by routine transvaginal ultrasound.