Babies conceived with assisted reproductive technology (ART) may be two to four times more likely to have certain birth defects (heart wall problems, gastrointestinal disorders, cleft lip/palate) than babies conceived naturally, according to a report published in the advance online edition of Human Reproduction.

“Today, more than 1% of infants are conceived through ART and this number may continue to increase. While the risk is low, it is still important for parents who are considering using ART to think about all of the potential risks and benefits of this technology,” said epidemiologist Jennita Reefhuis, PhD, of the US Centers for Disease Control and Prevention, lead author of the report.

ART refers to any procedure that involves surgically removing eggs from a woman’s womb, combining them with sperm in the laboratory, and returning them to the woman’s body or donating them to another woman. The procedure has been used in the US since 1980, and the number of infants born after ART doubled from 1996 through 2004. . In 2002, almost 12 percent of U.S. women ages 15 to 44 reported using infertility services. In 2005, more than 134,000 ART procedures were performed in the United States, resulting in the birth of about 52,000 babies, the CDC said.

For the study, Reefhuis and colleagues reviewed data from mothers of about 13,500 babies born with birth defects and mothers of more than 5,000 babies without birth defects. The study included only 281 women who had fertility procedures. The babies were born from October 1997- December 2003 in 10 states including Arkansas, California, Georgia Iowa, Massachusetts, New Jersey, New York, North Carolina, Utah and Texas. The study is among the first in the United States to analyze an association between infertility treatments and major structural birth defects.

Analyzing the babies conceived through ART, Reefhuis and colleagues found that there was twice the risk of heart defects, more than twice the risk of cleft lip and more than four times the risk of gastrointestinal defects when compared with babies conceived without fertility treatments. One example: the risk of a baby in the US being born with a cleft lip with or without a palate is above 1 in 950, but the study found that the risk is 1 in 425 for babies conceived through infertility treatments. Given the figures, the risk of a birth defect remains low, the researchers noted. However, it’s important for couples to be aware that thee may be some increased risk for birth defects as well, Reefhuis said.

The study did not evaluate artificial insemination or hormone treatments. Reefhuis also said that although her study linked fertility procedures to birth defects, it did not prove the connection or explain it. If the connection is real, it is not known whether the procedures increase the risk for birth defects, or whether infertility itself raises the risk.

Other researchers welcomed the findings although they said more research was needed to confirm them.

“The results are concerning, but with this small a sample of patients, a bigger study would need to be done. And the fact that they see it in singletons, not in twins, makes it hard for me to think this is a direct relationship,” Dr. James A. Grifo, director of the fertility clinic at New York University Medical Center, said.