Prevention of preterm parturition.

In the United States, the annual rate of preterm births (before 37 weeks of gestation) reached a peak of 12.8% in 2006 and was 11.7% in 2011.1 The rate in the United States remains nearly twice the rate in European nations.2 Premature birth in the United States accounts for 35% of deaths in the first year of life3,4 and estimated annual costs exceeding $26 billion.5 Rates of death in the first year of life and long-term morbidity such as neurobehavioral impairment are inversely related to gestational age at birth. Neonates born before 24 weeks of gestation rarely survive without serious handicaps. Among neonates born at or after 24 weeks of gestation, mortality and morbidity decline with advancing weeks of gestation. Serious neurodevelopmental complications are uncommon after 32 weeks of gestation; however, neonates born before 36 weeks of gestation often have difficulties with respiration, thermoregulation, and feeding, as well as increased risks of health problems and death in childhood.6 Approximately 25% of preterm births in developed nations are iatrogenic, reflecting cases in which maternal or fetal conditions make early delivery a safer choice than continued pregnancy, for the mother, the fetus, or both. Multifetal pregnancies account for about one fifth of all preterm births; 50% of twin births and more than 90% of triplet births are preterm. Most singleton preterm births occur after the spontaneous early onset of the parturitional process. This article focuses on strategies to prevent preterm birth.