Older women are having twins and other higher-order multiple births at an increasingly high rate, according to a new report by the National Center for Health Statistics, Centers for Disease Control and Prevention.

The report, "Trends in Twin and Triplet Births: 1980-97," shows that between 1980-82 and 1995-97 the twin birth rate rose 63 percent for women between the ages of 40 and 44 and nearly 1,000 percent for women 45-49 years of age. There were more twins born to women ages 45-49 in 1997 than during the entire decade of the 1980's.

At the same time, the triplet and higher birth rate rose nearly 400 percent for women in their thirties and exploded by more than 1,000 percent for women in their forties.

Overall, from 1980 to 1997 the number of twin births in the United States rose 52 percent (from 68,339 to 104,137) and triplet and higher births rose 404 percent (from 1,377 to 6,737 births). Comparable but less pronounced rises were observed in twin and triplet and higher birth rates.

Along the way, historical differences in twin birth rates between non-Hispanic white and black mothers have largely been eliminated. Non-Hispanic white women were more than twice as likely as non-Hispanic black or Hispanic women to have a triplet birth.

Rates of low birthweight, very low birthweight, and infant mortality were 4 to 33 times higher for twins and triplet and higher births compared with singleton births. The risk for these adverse outcomes was lowest for twins and triplet and higher born to women 35-44 years of age.

Twin birth rates for Massachusetts and Connecticut were at least 25 percent higher than the U.S. rate; triplet and higher birth rates for Nebraska and New Jersey were twice the national level.

© 1999