In discussing potential limits of the Iowa study, Van Voorhis noted that selection of the control group of naturally conceived babies was restricted to counties from which patients treated in the UI infertility clinic delivered their babies. Thus, it is possible that a small number of the "naturally conceived" controls were actually conceived using infertility treatment at another clinic.
"It's possible that focusing on our referral area underestimated the risk a little bit for IVF-conceived babies," Van Voorhis said. "In another consideration, some of the apparent increased risk in IVF babies could be the result of parents, doctors or both looking more carefully for birth defects, resulting in a slightly higher detection rate."
A known risk factor for major birth defects is a multiple birth -- in which there are twins, triplets or even more babies in one pregnancy. Multiple births have become more commonplace through IVF when two or more embryos are commonly transferred to a woman's uterus. However, a few centers, including UI Hospitals and Clinics, are more frequently implanting only one embryo in an IVF cycle to reduce the risk of multiple birth and the problems of premature delivery and birth defects.
"Overall, the study should reassure people that there is not a huge increased risk in using IVF. 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," Van Voorhis said.
In addition to Van Voorhis, the study included researchers in the Department of Obstetrics and Gynecology and the Department of Pediatrics in the UI Carver College of Medicine and the Department of Epidemiology in the UI College of Public Health.
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Contact: Becky Soglin
becky-soglin@uiowa.edu
319-335-6660
University of Iowa
30-Nov-2005