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Utah babies are more likely to be born with Down syndrome than in nine other states studied by the federal government.

The study, published online today in the American Academy of Pediatrics' journal Pediatrics , showed one in 730 babies born in Utah had the genetic disorder, compared with one in 848 among the 10 states studied.

The study didn't explore why. But a Utah expert on birth defects says it's likely because of Utah mothers' ages and attitudes.

Many continue to have children into their late 30s and 40s, which increases the risk of the chromosomal disorder, said Lorenzo Botto, a medical epidemiologist at the Utah Birth Defect Network, which provided data for the study.

And Utah women are less likely to have abortions once the condition has been detected prenatally, he added.

The higher prevalence is "not because there is something wrong with Utah," he said in an e-mail, "but is basically a function of family choices."

Amy Moore, whose 14-year-old daughter has Down syndrome, was not surprised by Utah's ranking. When she lived here -- she now lives in Wyoming -- Kenly had friends with the condition and Moore had a larger support system.

Moore said her teenager is a cheerleader, swims and after years of speech therapy can "say whatever is on her mind, for better or for worse. She's nothing but a blessing in our lives."

The Centers for Disease Control and Prevention gathered data from 10 birth defect surveillance systems to provide the first large-scale prevalence estimates in the United States. Down syndrome, a condition caused by an extra copy of the 21st chromosome, is the most common chromosomal disorder.

The number of people living with Down syndrome is expected to increase because more are being born, surviving beyond age 5 and dying at a later age -- 60 instead of 25, the life expectancy in the 1980s. In addition to having cognitive delays, they are at a greater risk for health conditions such as congenital heart defects and respiratory, hearing and thyroid problems. Most of the problems can be corrected.

It helps to know their numbers in order to plan for their care, the study says.

From 1999 to 2003, the study shows the prevalence of Down syndrome at birth was 11.8 babies per 10,000 live births. In Utah, the prevalence was 13.7. Arkansas had the lowest, at 9.7. Nationally, the prevalence is highest among male and Latino babies.

The study also found that the prevalence at birth among the 10 states increased by 31 percent from 1979 to 2003. That parallels the increase in the number of births to women older than 35.

The risk of Down syndrome increases with maternal age, though 80 percent of babies with Down syndrome are born to younger women because they have a higher fertility rate.

In Utah, the prevalence was nearly seven times higher among births to older mothers than among younger ones.

"More [Utah] women are having more kids in their higher 30s and lower 40s," Botto explained.

Of the 55,000 Utah births in 2007, nearly 10 percent of the babies were born to women ages 35 and older, according to data from the Utah Department of Health.

Based on the study, Botto estimates there are 1,000 Utah children living with Down syndrome.

"It's important to recognize how common it is," said Lisa Samson-Fang, a pediatrician who treats some of the children. She wasn't associated with the study but said it could be helpful to improve services to those children. One of her top concerns is helping adults find doctors who are able to handle their complex health problems.

In addition to Utah, the study analyzed data from Arkansas, Georgia, California, Colorado, Iowa, North Carolina, New York, Oklahoma and Texas." Target="_BLANK">

What is Down syndrome?

Down syndrome is a chromosomal disorder caused by the presence of an extra copy of the 21st chromosome. In addition to having cognitive delays, people with Down syndrome are at increased risk for health conditions such as congenital heart defects and respiratory, hearing and thyroid problems.