Unlike newborn adoption, where the biological mother assumes the risks of pregnancy and childbirth, embryo adoption turns the tables and places the risk of miscarriage, still birth, birth defects, and the possibility of a difficult delivery upon the adopting mother. Because most people decide to transfer two or more embryos at a time to increase their chances of conception, the chance of a multiple pregnancy (twins and triplets) and all the associated complications come with it.
Uncertainty is another risk. When a couple chooses traditional adoption, in the vast majority of cases, they will eventually bring home a child. But embryo adoption is no guarantee. Only two-thirds of frozen embryos survive the thawing process, and of the ones that are viable for implantation into a mother, the chances of conception are still only around 30 to 35 percent per attempt. Conaghan says, "About one in three women who has embryos to adopt will go home pregnant." Because of those odds, Oakley adds, "Most families will need to do more than one transfer to achieve pregnancy. At the NEDC, adoptive parents make first, second, and third choices of donated embryos in case the initial attempt doesn't work."