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Frozen or fresh, IVF embryos equal in live births
After the first completed cycle of IVF, ongoing pregnancy occurred in 36% of women in the frozen embryo group, and in 35% of the fresh embryo group. Rates of live birth after the first embryo transfer were 34% in the frozen embryo group, and 32% in the fresh embryo group.
"Previous research has shown that women who experience infertility because of PCOS benefit from significantly higher live birth rates from frozen embryos in IVF procedures, but evidence was lacking for this approach in non-PCOS patients."
The study, however, did find that frozen-embryo transfers resulted in a significantly lower risk of ovarian hyperstimulation syndrome (OHSS) than women using fresh-embryo transfers. While most cases of the syndrome are minor, severe cases can lead to illness and even death. Women using frozen embryos were found to have a 0.6% chance of developing OHSS, versus a 2% chance for women receiving fresh embryos.
This is an emerging issue of immediate and important concern for couples who are seeking in-vitro fertilization treatment,
Professor Mol feels that while many clinics are moving completely away from fresh embryo transfers, the freezing process adds additional costs in IVF and does not result in higher rates of live births. "Couples concerned about such unnecessary costs of freezing all embryos do not need to go down that path, and will still have the same live birth success rate,". Dr Vuong: "Our research results are specific to a common freezing method known as Cryotech vitrification, so it may not apply to all embryo freezing techniques currently being used. Further research will be needed to compare pregnancy outcomes and live birth rates from other embryo freezing techniques."
There is a strong collaboration between the Adelaide, Australian group and Vietnamese researchers to capitalize on this research.
Among women who are undergoing in vitro fertilization (IVF), the transfer of frozen embryos has been shown to result in a higher rate of live birth than the transfer of fresh embryos in those with infertility associated with the polycystic ovary syndrome. It is not known whether frozen-embryo transfer results in similar benefit in women with infertility that is not associated with the polycystic ovary syndrome.
We randomly assigned 782 infertile women without the polycystic ovary syndrome who were undergoing a first or second IVF cycle to receive either a frozen embryo or a fresh embryo on day 3. In the frozen-embryo group, all grade 1 and 2 embryos had been cryopreserved, and a maximum of two embryos were thawed on the day of transfer in the following cycle. In the fresh-embryo group, a maximum of two fresh embryos were transferred in the stimulated cycle. The primary outcome was ongoing pregnancy after the first embryo transfer.
After the first completed cycle, ongoing pregnancy occurred in 142 of 391 women (36.3%) in the frozen-embryo group and in 135 of 391 (34.5%) in the fresh-embryo group (risk ratio in the frozen-embryo group, 1.05; 95% confidence interval [CI], 0.87 to 1.27; P=0.65). Rates of live birth after the first transfer were 33.8% and 31.5%, respectively (risk ratio, 1.07; 95% CI, 0.88 to 1.31).
Among infertile women without the polycystic ovary syndrome who were undergoing IVF, the transfer of frozen embryos did not result in significantly higher rates of ongoing pregnancy or live birth than the transfer of fresh embryos. (Funded by My Duc Hospital; ClinicalTrials.gov number, NCT02471573.)
Authors: Lan N. Vuong, M.D., Ph.D., Vinh Q. Dang, M.D., Tuong M. Ho, M.D., Bao G. Huynh, M.Sc., Duc T. Ha, M.D., Toan D. Pham, B.Sc., Linh K. Nguyen, M.D., Robert J. Norman, M.D., and Ben W. Mol, M.D., Ph.D.
Supported by My Duc Hospital, Ho Chi Minh City, Vietnam.
From the Department of Obstetrics and Gynecology, University of Medicine and Pharmacy at Ho Chi Minh City (L.N.V.), IVFMD, My Duc Hospital (L.N.V., V.Q.D., T.M.H., B.G.H., T.D.P., L.K.N.), and the Research Center for Genetics and Reproductive Health, School of Medicine, Vietnam National University (T.M.H.), Ho Chi Minh City, and the National Hospital of Can Tho, Can Tho (D.T.H.) all in Vietnam; and the Robinson Research Institute, Department of Medicine (R.J.N., B.W.M.), Fertility South Australia (R.J.N.), and the South Australian Health and Medical Research Institute (B.W.M.) all in Adelaide, SA, Australia. Return to top of page
A twelve cell embryo under magnification. IVF transfer of embryos usually occurs following multiple divisions, approximately after Carnegie Stage 2, in order to assess the quality of the embryo. Transfer to the mother may be anytime between day 1 through day 6 after egg retrieval, although it is usually between days 2-4. Some clinics are now allowing the embryo to reach blastocysts stage before transferring, which occurs around day 5. Image credit: © stock.adobe.com