An Australian study published in the New England Journal of Medicine finds Assisted Reproduction Technologies (ART) substantially increase birth defect risks.
"The unadjusted risk of any birth defect in pregnancies involving assisted conception was 8.3% (513 defects), compared with 5.8% for pregnancies not involving assisted conception (17,546 defects)," Associate Professor Davies says.
"The risk of birth defects for IVF was 7.2% (165 birth defects); and the rate for ICSI was higher at 9.9% (139 defects).
"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% increase in the odds of major defect, although the absolute size of the risk remained relatively small," he says.
Of course the researchers tried to adjust for other causes of defects. For example, older women have greater risks of birth defects even without using ART. But note that since we do not all age at the same rate the women who need ART in order to conceive probably have effectively older reproductive tracts than other women at the same age who are still fertile.
But use of cryopreservation is associated with a reduction in risk of birth defects.
Associate Professor Davies says 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," he says.
That's encouraging because it suggests better technologies for embryo selection could lower the rate of birth defects.
A drug that stimulates ovulation raises birth defect risks.
Also of concern was the tripling of risk in women using clomiphene citrate to stimulate ovulation outside of a closely supervised clinical setting.
I expect ART will eventually advance to the point where it will enable lower rates of birth defects than occur naturally. This will happen a few ways:
Note that even for younger women smarter embryo selection will some day make the use of assisted reproduction technologies preferable to the natural way to start pregnancies. ART will lower birth defect rates while also providing the ability to select for embryos that have desired combinations of genetic traits from the two (or more) genetic parents.
|Share |||Randall Parker, 2012 May 20 11:13 PM Biotech Reproduction|