Three Decades of Twin Births in the United States, 1980-2009

摘要

The incidence of multiple births in the United States was quite stable at about 2 percent of all births from 1915 (the earliest year for which reliable data are available) through the 1970s. By the early 1980s, however, twinning rates, and those for triplet and higher-order multiples (triplet/+) began to rise, ultimately leading to what has been called an epidemic of multiple pregnancies. The marked increase in multiple births is important for reasons beyond their relative rarity. Plural pregnancies tend to exact a greater toll on the health of the mother, and outcomes for births in multiple deliveries are often compromised compared with singletons. The rise in the rate of twins, which comprise the majority of multiples (96 percent in 2009), has had an unfavorable impact on key indicators of perinatal health such as rates of preterm birth and low birthweight. This report describes U.S. trends in births in twin deliveries for the 30-year period 1980-2009.