A new study by researchers at the University of Adelaide, Australia, has quantified the risk of major birth defects associated with different types of assisted reproductive technology.
In the most comprehensive study of its kind, the researchers compared the reproductive therapies commonly available: IVF (in vitro fertilization), ICSI (intracytoplasmic sperm injection) and ovulation induction. They also compared the risk of birth defects after fresh and frozen embryo transfer.
The results, published in the New England Journal of Medicine, showed that while assisted reproductive technologies are associated with an increased risk of major birth defects there were significant differences in risk between available treatments.
The findings showed that the risk of any birth defect in pregnancies involving assisted conception was 8.3 percent, compared with 5.8 percent for pregnancies not involving assisted conception. Specifically, the risk of birth defects for IVF was 7.2 percent and the rate for ICSI was higher at 9.9 percent.
"A history of infertility, either with or without assisted conception, was also significantly associated with birth defects. While factors associated with the causes of infertility explained the excess risk associated with IVF, the increased risk for a number of other treatments could not readily be explained by patient factors. ICSI, for instance, had a 57 percent increase in the odds of major defect, although the absolute size of the risk remained relatively small," said the study's lead author Associate Professor Michael Davies.
Interestingly, cryopreservation (freezing) of embryos was associated with a substantially reduced risk of birth defects, particularly for ICSI. "This may be due to developmentally compromised embryos failing to survive the freeze/thaw process," Davies says.
Also of concern was the tripling of risk in women using clomiphene citrate to stimulate ovulation outside of a closely supervised clinical setting. "This is of particular concern as clomiphene citrate is now very widely available at low cost, and may easily be used contrary to manufacturers' very specific instructions to avoid use if pregnant, as it may cause fetal malformations. This aspect of the study will need additional confirmation from future research," Davies noted.
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Source: University of Adelaide