Progesterone for preterm birth prevention.

Preterm birth—delivery before 37 weeks of gestation—is the second leading cause of infant mortality in the United States after congenital malformations. Spontaneous preterm birth, due to either preterm labor or preterm premature membrane rupture, encompasses approximately 75% of all preterm births, almost 400,000 births per year. Since the 1960s, different formulations of progesterone have been investigated for preterm birth prevention. This article addresses the use of progesterone for the prevention of preterm birth, including selection of candidates for progesterone, pharmacokinetics, dosing, and formulations. This article aims to provide a practical guide for using progesterone in clinical practice.