Objectives: This report describes changes in the number and ratio of live births in triplet and other higher order multiple deliveries from 1971 to 1994 by maternal race, age, education, and marital status. The report also examines the birth outcomes of triplets compared with singletons, including overall gestation specific, and birthweight specific infant mortality rates.
Methods: Birth data are obtained from the U.S. certificates of live birth. Mortality data were obtained from the Linked Birth and Infant Death Data Sets for the 1983-91 birth cohorts. Most analyses are based on triplet and other higher-order multiple births (quadruplet and quintuplet and greater births) in the aggregate. (Triplet births comprise about 92 percent of all higher order multiple births.) Triplet and other higher order birth ratios for most variables are computed by combining data for years 1982-84 and 1992-94, and for infant mortality by combining birth cohorts for years 1987-91.
Findings: Between 1971 and 1994 the number and ratio of triplet births quadrupled, rising from 1,034 to 4,594, and from 29.1 to 116.2 per 100,000 live births. Most of the increase was among births to white mothers, particularly among married and more educated mothers. Only about one-third of the increase in triplet birthing among white mothers between 1989 and 1994 could be attributed to changes in the maternal age distribution. Massachusetts reported the highest triplet birth ratio (215.9), more than twice the U.S. ratio (105.5). Other States with comparatively high ratios were New Hampshire, New Jersey, and Iowa. Nine of 10 triplets were born preterm compared with 1 of 10 singletons. The average triplet weighed 1,698 grams at birth, one-half that of the average singleton (3,358 grams). Triplets were about 12 times more likely to die during the first year of life as singletons, but had a survival advantage over singletons at lower gestations and birthweights.