Preterm birth is the leading cause of neonatal mortality and a major public health concern. Risk factors for preterm birth include a history of preterm birth, short cervix, infection, short interpregnancy interval, smoking, and African-American race. The use of progesterone therapy to treat mothers at risk for preterm delivery is becoming more widespread. Tocolytics may not prevent preterm birth but have a role in prolonging pregnancy for administration of medications to benefit the preterm infant. These include antenatal steroids and, if indicated, magnesium sulfate for neuroprotection and intravenous antibiotics for Group B Streptococcus prophylaxis.