RESUMEN
In the United States, preterm delivery is the leading cause of neonatal morbidity and is the most common reason for hospitalization during pregnancy. The rate of preterm delivery (before 37 weeks' gestation) has been declining since 2007. Clinical diagnosis of preterm labor is made if there are regular contractions and concomitant cervical change. Less than 10% of women with a clinical diagnosis of preterm labor will deliver within seven days of initial presentation. Women with a history of spontaneous preterm delivery are 1.5 to two times more likely to have a subsequent preterm delivery. Antenatal progesterone is associated with a significant decrease in subsequent preterm delivery in certain pregnant women. Current recommendations are to prescribe vaginal progesterone in women with a shortened cervix and no history of preterm delivery, and to use progesterone supplementation regardless of cervical length in women with a history of spontaneous preterm delivery. Cervical cerclage has been used to help correct structural defects or cervical weakening in high-risk women with a shortened cervix. A course of corticosteroids is the only antenatal intervention that has been shown to improve postdelivery neonatal outcomes, including a reduction in neonatal mortality, intracranial hemorrhage, necrotizing enterocolitis, and neonatal infection. Tocolytics, especially prostaglandin inhibitors and calcium channel blockers, may allow time for the administration of antenatal corticosteroids and transfer to a tertiary care facility if necessary. When used in specific at-risk populations, magnesium sulfate provides neuroprotection and decreases the incidence of cerebral palsy in preterm infants.