One of the largest studies ever conducted in the U.S. shows that infants conceived from infertility treatments are two-to-four times more likely to have certain birth defects than children conceived the classic way.

The defects are surgically treatable. They include heart anomalies, cleft lips and gastrointestinal disorders.

"None of these are lethal," said study co-author Dr. Jennita Reefhuis, an epidemiologist with the federal Centers for Disease Control and Prevention. "The individual risk of birth defects is still very small. But it is very important for couples who are considering artificial reproductive technology to have full disclosure."

The study, published in the journal Human Reproduction, says that nearly 12 percent of U.S. women have undergone infertility treatments as more and more couples look to them to help with conception. One percent of all U.S. births, twice as much as in 1996, occur as results of the treatments. In 2005, more than 134,000 couples resorted to the procedure, and 52,000 births were the result. Although generally considered risky, the study is one of the first to conclusively associate infertility treatments with major birth defects.

Data shows that the risk of heart defect doubles, as does the risk of cleft lip/palate, while the risk of gastrointestinal defects quadruples for babies conceived through the treatments, compared to naturally conceived babies.

Data from 281 assisted births and 14,095 natural births was analyzed, but no reason for the higher rate of birth defects associated with the technology was given.

"We don't know if it's the treatment or the underlying condition of infertility," said Suzan Carmichael, an epidemiologist with the March of Dimes California Research Division, at the Children's Hospital and Research Center at Oakland.

Independent studies in Europe have shown similar risk rates.