What Happens to Leftover Frozen Embryos?

Frozen human embryos are checked at the Priory Hospital in Birmingham, England. (Reuters)

Couples who have frozen embryos left over after undergoing in-vitro fertilization (IVF) are more likely to donate them to other infertile couples if the embryos were conceived with a donated egg, new research shows.

The study also shows that most couples who did have extra frozen embryos after IVF - whether or not they were from donated eggs - either used the embryos in subsequent rounds of IVF or chose to continue to store them, Dr. Melanie R. Freeman and Dr. George A. Hill of the Nashville Fertility Center in Nashville, Tennessee, report in the journal Fertility and Sterility.

"The real problem is that there are not enough embryos donated for people who want to accept them and get pregnant from them," Freeman told Reuters Health. Only a few infertility clinics offer the option of donating an embryo, or becoming pregnant with a donated embryo, she added. At the Nashville Fertility Center, pregnancy success rates with donated frozen embryos range from 42 percent to 50 percent, Freeman and Hill note in their report.

Center policy requires couples to state their wishes for the disposition of extra embryos before undergoing an IVF cycle, and then provide consent a second time before disposition actually takes place.

To investigate the choices couples made, and whether or not having conceived an embryo with a donated egg made any difference, the researchers looked at records from 1998 to 2008 for 1,262 patients who used their own eggs and had 5,417 embryos preserved, and another 272 patients who conceived with donated eggs and preserved 1,233 embryos.

Among the couples who conceived with their own eggs, 39 percent used the stored embryos and 35 percent decided to keep the embryos in storage, while 40 percent of the couples who used donated eggs used the embryos and 23 percent continued to store them.

And among the 364 patients who used their own eggs and had embryos left over, 21 percent donated them to infertile couples, 11 percent donated them for research, and 68 percent discarded them.

Among the 110 patients with extra embryos who had conceived via egg donation, 56 percent gave the embryos to other infertile couples, 6 percent donated them for research, and 38 percent discarded them.

According to Freeman, it's not surprising that the egg donor recipients would be more likely to donate their embryos in turn. "The people using donated eggs had someone donate to them, so I guess they turn around and are altruistic and donate to someone else," she said.

"We really need to educate patients on this alternative," Freeman added. "I think it's a good choice. If we had more embryos, it would be a great choice for a lot of people."