CDC: Down syndrome more common than thought

ATLANTA - A new report finds that Down syndrome is more prevalent than previously thought.

The new report - released Thursday - offers the most reliable prevalence estimates to date of 18 types of birth defects, federal officials said.

Among the findings: Down syndrome occurs at a rate of about one in every 733 live births. It was previously estimated to occur in a range of from one in every 800 to one in every 1,000.

In addition, cleft lip occurs in about one in every 1,000 births, and cleft palate in about one in very 1,500, according to the report.

The report, published in the federal Centers for Disease Control and Prevention's Morbidity and Mortality Weekly report, was celebrated by advocacy groups that help families affected by birth defects. They noted the new numbers are based on statewide data, and are considered more solid than the previous prevalence estimates, which were derived from reports from an incomplete list of clinics and hospitals.

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

The better numbers may help advocates develop public education campaigns, push for additional research and plan client services, Armstrong and others said.

From 1974 until the mid 1990s, the government routinely tracked birth defects through a system that relied on discharge reports from certain hospitals.

But the system was flawed, researchers said. Not all hospitals were represented, and it's possible reporting hospitals attracted more problematic births than the norm - or the reverse.

In 1997, the government initiated a population-based system, which sends data abstracters to all the birth hospitals in studied geographic areas, as well as specialty clinics and referral centers for birth defects.

The new report presents statewide data for Arkansas, Hawaii, Iowa, Massachusetts, North Carolina, Oklahoma, Texas and Utah. It also has data from specific regions in three other states - the metro Atlanta area in Georgia, the Central Valley in California and a group of counties in southern Alabama.

The data is for the years 1999 to 2001.

The 11 states account for about 22 percent of all the live births in the United States each year, and are considered a good representative sample, said Joann Petrini, a study co-author, who is director of the March of Dimes' perinatal data center in White Plains, N.Y.

But the data is far from complete. "It's a start," Petrini said.

The researchers included only 18 of the thousands of birth defects that have been identified by doctors and scientists.

Missing from the list are traditionally common birth defects such as clubfoot, hip dislocation and hypospadias - a condition in which a boy's urination opening is located on the underside of the penis instead of the tip.

In the new study, researchers only included conditions that were commonly identified at or right after birth and consistently diagnosed and treated from hospital to hospital. Hypospadias, which can be mild or severe, and didn't fit that standard, explained Margaret Honein, a CDC epidemiologist and study author.

Spina bifida was not included either, because health officials already have what they consider reliable prevalence estimates on that condition, she added.

In the case of Down syndrome, advocacy groups for the last ten years have used estimates that were based on reports from selected clinics and hospitals, Armstrong said.

The number is old, but it's not known if the prevalence rate of Down syndrome has changed since then.

The risk of Down syndrome increases with the age of the mother, from an estimated 1 in 2,000 for 20-year-old women to 1 in 100 for women age 40. Recent societal trends suggest larger numbers of women having babies later in life, which might explain a higher prevalence rate in recent years.

But because the new data was collected differently, and apples and oranges comparison is difficult, Armstrong and others said.