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Health and medicine

Prevalence of Down's syndrome rethought

The condition is more common than previously estimated, a federal report on birth defects finds.

ATLANTA - Down's syndrome in the United States is more common than previously thought, at one case for every 733 live births, according to a new government report containing what are regarded as the most reliable estimates yet on the prevalence of 18 types of birth defects.

Previously, Down's syndrome, a type of retardation caused by a genetic mutation, was estimated to occur in a range of one in every 800 live births to one in 1,000.

The report, released Thursday by the Centers for Disease Control and Prevention, also found that cleft lip occurs in about one in every 1,000 births, and cleft palate in about one in every 1,500.

The report was celebrated by advocacy groups that help families affected by birth defects. They noted that the new numbers are based on statewide data from eight states as well as data from communities in three other states, while previous estimates were derived from selected clinics and hospitals. The statistics are for the years 1999 to 2001.

"Until now, there's been a real dearth of good, reliable, national statistics on Down's syndrome," said Suzanne Armstrong, spokeswoman for the National Down Syndrome Society.

The risk of Down's syndrome increases with the mother's age, from an estimated 1 in 2,000 among 20-year-old women to 1 in 100 for women age 40. Many women are having babies later in life, which might explain the higher rate in the new study. But because the new statistics were not collected in the same way as the old, it is not clear whether Down's syndrome has really increased, Armstrong and others said.

[Last modified January 6, 2006, 01:05:09]