In a Vietnamese study, rates of live births after the first transfer were comparable between groups: 33.8% with frozen embryos and 31.5% with fresh embryos, according to Lan N. Vuong, MD, PhD, of the University of Medicine and Pharmacy at Ho Chi Minh City, and colleagues. Frozen-embryo transfer has shown promise as a superior method of IVF compared to fresh-embryo transfer, demonstrating higher live-birth rates and lower rates of pregnancy loss in small-scale observational studies.
In the Chinese study of 2,157 women undergoing their first in-vitro fertilization cycle, the birth rate was 48.7 percent with thawed embryos and 50.2 percent with fresh.
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.
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.
Many women struggling to have a baby turn to in-vitro fertilization to improve their chances, and then face further uncertainty and anxiety when confronted with the decision of whether to use frozen or fresh embryos. He's a professor of obstetrics and gynecology and public health sciences.
But it's not clear whether frozen-embryo transfer would hold the same benefit in ovulatory women with infertility, who don't have PCOS.
Neither study found a higher risk of neonatal or obstetrical complications in either group, although frozen embryo transfer produced a statistically lower risk of over-stimulated ovaries, which leads to swollen and painful ovaries and is potentially unsafe. In those cases, fertility experts believe that freezing the embryos to give the woman time between when the eggs are extracted and fertilized, after she has received hormones to produce more eggs than her normal cycle would, may provide a more receptive uterine environment for an embryo to grow.
It was her frozen embryos that gifted her two daughters, Melissa, now 20 years old, and Ashley, 17. This could challenge the long-held belief of fertility specialists that freezing and thawing embryos before implanting them offers a better chance of successful pregnancy and birth. Using block randomization, they assigned the women to either fresh-embryo transfer or embryo cryopreservation followed by frozen-embryo transfer.
"We shouldn't be freezing embryos across the board [for all IVF cycles] if it makes no difference", says Dr. Christos Coutifaris, president of the American Society for Reproductive Medicine and chief of reproductive endocrinology at University of Pennsylvania, who was also not involved in the study.
After the first fresh embryo transfer, it will be possible to freeze the remaining embryos and transfer them one by one, if necessary, without reducing the chance of pregnancy.
"And that's reassuring for people who do a lot of frozen embryo transfer, which most of us are doing".
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