For most women undergoing in vitro fertilization, fresh embryos work just as well as frozen ones.
Previous trials have suggested that using only frozen embryos might improve pregnancy rates in women with polycystic ovary syndrome, or PCOS, a hormonal disorder that affects about 10 percent of women. (Women with this condition ovulate irregularly and typically have a poorer response to IVF treatment.) But in two large randomized trials published in the New England Journal of Medicine, researchers found using fresh or frozen embryos makes no difference for the majority of women who do not have PCOS.
In the first study, of 2,157 women without PCOS, 50.2 percent of fresh embryo transfers resulted in a live birth, and so did 48.7 percent of the frozen transfers. The difference was statistically insignificant.
In the second, of 782 women without PCOS, live birthrates were 33.8 percent for the frozen-embryo group and 31.5 percent for the fresh, again an insignificant difference.
“Unless there are specific factors that require it, you can safely go with a fresh transfer of your first embryo,” said the senior author of the second study, Dr. Ben W. Mol, a professor of obstetrics at the University of Adelaide in Australia. “Transfer your first embryo fresh. There is no need to completely go around the first fresh transfer.”
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