ABSTRACT
The delivery of infants prior to 37 weeks of gestation complicated 12.3% of births in the United States (US) in 2003, and was the leading cause of neonatal morbidity and mortality.1 The US preterm delivery (PTD) rate has climbed 14% during the past 15 years, reflecting both a 40% rise in multifetal pregnancies and an increase in prematurity among women with singleton gestations from 9.7 to 10.4%.2 Racial and ethnic disparities exist in the US PTD rate with 11% of nonHispanic white births and 17.7% of non-Hispanic black births occurring preterm.2 Comparable increases in PTD rates have been observed in Europe, though overall rates tend to be lower than in the US (e.g. 6.9% in Denmark).3 Antecedents to PTD include those indicated by deteriorating maternal or fetal health, which account for about 25% (range 18.7-35.2%) of cases, and spontaneous PTD, which either follow preterm premature rupture of membranes (PPROM) (30%; range 7.1-51.2% of cases), or spontaneous preterm labor with intact fetal membranes (PTL) (45%; 23.2-64.1% of cases).4 This review will focus on the latter two categories.
