Infants born to couples who underwent assisted reproduction face a slightly higher risk of birth defects compared to babies conceived naturally, claims a new study.1 But the authors of the research are quick to add that this does not prove that in vitro fertilization (IVF) and other forms of assisted reproductive technologies (ART) are the causes. It could be directly related to the parents' infertility, the investigators at the University of Iowa stress.
Some of the birth defects found in the study include those of the heart, muscle or skeletal system.
Underlying Cause Unknown
The risk of these genetic abnormalities was about 6% for babies born after ART compared to about 4.5% for children born to mothers who became pregnant through other means. While the findings do not necessarily suggest that there's a relationship between ART and birth defects, it's important to address because nearly 1 percent of all children born in the United States are conceived using in vitro fertilization, explained Brad Van Voorhis, MD, a professor of Reproductive Endocrinology at the university, and the study's lead researcher.
"The finding indicates that the vast majority of IVF-conceived babies are not affected by major birth defects," Van Voorhis said. "Most appear to be fine, at least up to age 1, which was our study limit. However, the question remains whether the slight increased risk for IVF babies is caused by the treatment itself, by factors in infertile couples who seek IVF, or by some combination of the treatment and these factors."
Comparing ART Procedures and Birth Defects
Van Voorhis and his team collected information on ART performed between 1989 and 2002 from records maintained at the University of Iowa Hospitals and Clinics. Records on birth defects from the Iowa Registry for Congenital and Inherited Disorders were also collected for the research.
The data revealed major birth defects in 90 of nearly 1,500 IVF-conceived children, 17 of 343 children conceived using intrauterine insemination (IUI) and 369 of more than 8,000 naturally conceived children. There were about 6% of IVF cases that involved birth defects, 5% of IUI cases, and nearly 4.5% of cases involving natural conception.
Van Voorhis explained that the researchers studied babies born from assisted reproductive techniques aside from IVF to determine if the increased risk was linked with the IVF procedure or factors in couples treated for infertility.
"Had we seen a lower risk for IUI-conceived babies, suggesting that another form of assisted reproduction had no increased risk compared to natural conception, it might have pointed toward IVF as a culprit," Van Voorhis explained. But the risk of major birth defects was slightly higher for IUI babies than for those naturally conceived."
Questions Still Remain
If the birth defect risk had been higher for IUI babies than for those conceived following IVF, it would have been assumed that the risk was linked with some factor related to the parents' infertility, he said. "Yet the IUI rate was in between the rates for IVF and natural conception, so it remains unclear."
The increased risk for IVF babies could be blamed on a combination of both the procedure itself and some factor related to the parents' underlying infertility, he stated, though that hasn't been confirmed.
"We are not trying to assign 'blame' for the problem, but rather are hoping to pinpoint areas of the IVF treatment that could be changed to improve the safety for children," Van Voorhis said, adding that it would take a much larger study involving multiple states and patient record databases to answer questions about the cause of these increased birth defect risks.
One known risk factor for birth defects is a multiple pregnancy, such as twins or triplets. But while multiple births have become more common in IVF procedures in the last several years, fertility clinics are increasingly transferring only one embryo per cycle to reduce the risk of multiple pregnancy.
"Overall, the study should reassure people that there is not a huge increased risk in using IVF," explained Van Voorhis. "However, at centers like ours, we are always careful in our practice of assisted reproduction, and studies like this indicate treatment needs to be done in specialized centers that pay attention to these types of concerns."
1. Olson CK, Keppler-Noreuil KM, Romitti PA et al. In vitro fertilization is associated with an increase in major birth defects. Fertil Steril 2005 Nov;84(5):1308-45.
John Martin is a long-time health journalist and an editor for CuraScript. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.