The recent meeting of the European Society of Human Reproduction and Embyrology (ESHRE) in Stockholm included two European studies – one from France, another from Denmark – indicating that babies born after a frozen embryo transfer, rather than one using fresh embryos, are both larger and heavier. The risk for a baby to be heavy for its gestational age at birth is increased 1.6-fold compared to IVF children from fresh embryo transfer and 1.5-fold compared to naturally conceived children, said a press release.
The French study found that height, weight, and head size were all greater in “cryo babies” (those born from a frozen embryo) compared to “fresh babies." Says Dr. Sylvie Epelboin, from Bichat-Claude Bernard Hospital, in Paris, “we are not sure why the cryo babies are heavier and larger, but we think it may have something to do with the hormonal hyperstimulation during the fresh cycles.” The mean birthweight of frozen-embryo babies was 102 grams – about 3.6 ounces – greater than fresh-embryo babies.
“Cryopreservation of embryos can result in ‘Large Offspring Syndrome’,” said Dr. Anja Pinborg of the Rigshospital at Copenhagen University, in Denmark, in a press release. Pinborg and her colleagues conducted the second study, tracking 910 singleton births from frozen embryos with 9,603 babies from fresh embryos and 4,656 children born from natural conception. Nearly 17% of fetuses from frozen transfer were large for their gestational age, versus 11% of naturally conceived fetuses.
While it is of course a good thing for babies to be a healthy weight at birth, the study authors note that a high birth weight tends to increase the odds a woman will need a Caesarean section to deliver her baby and may increase the need for intervention, as well as the chances for complications in labor and delivery.