Infertility Treatments May Raise Birth Defect Risk
Study Finds Certain Kinds of Assisted Reproduction Are Linked to Higher Rates of Birth Defects
Tracking Birth Defects After Fertility Treatments continued...
One important point: When the doctors adjusted their data to account for a host of medical conditions and circumstances that are known to raise the risk of birth defects, like the mother's age and a history of smoking, the increased risks associated with IVF largely went away -- suggesting that the procedure itself was not to blame.
Birth defects associated with ICSI, however, remained 55% higher than the rates seen in fertile couples even after researchers took into account underlying factors associated with birth defects.
Despite the apparent increased risk, "people getting ICSI shouldn't be immediately alarmed," says Davies.
"The [newest] data in the study are now 10 years old, and in that time, there have been dramatic improvements in implantation rates in ICSI, which I take to mean that embryo quality has improved over that time. So it could be that we're looking at a historical snapshot and technology has overtaken it somewhat," he says.
Freezing Embryos May Lower Birth Defect Risk
In looking even more closely at the numbers, Davies says there also seemed to be a difference in the risk of birth defects depending on whether doctors were working with fresh, as opposed to previously frozen, embryos.
Babies conceived from embryos that were frozen after ICSI have a risk of birth defects that's nearly the same as that of babies born to fertile couples. Whereas babies that started as fresh embryos had a risk of birth defects that was about 75% higher than those born to fertile couples.
"The freeze-thaw cycle improves risk," Davies says. "The birth weights and gestations also improve after freezing."
That may be because embryos that survive freezing are simply healthier to begin with and more likely to develop normally, he says.
"I think it's probably an [indicator] of embryo quality," Davies tells WebMD. "There's quite a loss of embryos during the freeze-thaw cycle. What's interesting is that it may be the ones that are not developmentally competent anyway."
Other treatments associated with higher risks of birth defects included gamete intrafallopian transfer (GIFT), which involves mixing an egg and sperm in a test tube and then immediately placing the mixture into a fallopian tube. GIFT was tied to a 73% increased risk of birth defects, but experts say it is less of a concern because it's rarely used anymore.
Researchers Warn Against Self-Dosing Clomid
The highest risk associated with any treatment was seen with the at-home use of the drug clomiphene citrate, or Clomid, which stimulates ovulation.
Fertility doctors know to carefully time the dosing of Clomid so that it stimulates ovulation but is cleared from the body before a woman becomes pregnant.
"It's not a drug that a fetus wants to be exposed to," says Davies. "It stops the growth of new blood vessels, but that's not necessarily what we want to happen in a developing fetus."