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Frozen vs. fresh embryos for IVF? Study finds little impact on fertility

12 January 2018

Be aware that these trials were in women without polycystic ovarian syndrome.

After an earlier study by the Chinese team showed that frozen embryos were better for women with PCOS, "a lot of people jumped to the conclusion that we should always do frozen".

"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", one of the studies concluded.

The study, released by the University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI) and University of Medicine and Pharmacy at Ho Chi Minh City on Thursday, found that the ongoing pregnancy rates and live births in IVF women were similar from frozen and fresh embryos.

But whether frozen embryos contributed to the same pregnancy and live birth rates as fresh embryos wasn't clear.

"The cost for freezing embryos is about 30 percent more than that for fresh transfer", said Dr. Vuong.

Both studies were published online in the New England Journal of Medicine.

The researchers found that women using frozen embryos had a live birth rate of 48.7%, versus a live birth rate of 50.2% for women in the group where the embryos weren't frozen.

"The importance of these papers is that it documents what we know", says Dr. Jamie Grifo, program director of the New York University Fertility Center, who was not involved with the studies.

For their study, Chen and colleagues enrolled women at 20 clinical sites across China between March 2015 and November 2015. The resulting embryo is then inserted in the woman's uterus.

But until now, it was not known whether this was also the case for women confronted with fertility problems due to other reasons. Each woman received up to two cleavage-stage embryos. Secondary outcomes included rates of pregnancy complications (ovarian hyperstimulation syndrome, ectopic pregnancy, congenital anomaly), birth weight, rates of pregnancy loss, and comparisons of biochemical pregnancy and clinical pregnancy characteristics. Additionally, the embryos were transferred at cleavage stage in order to minimize the risk of arrested embryo development leading to no embryo transfer.

Li Peng Monroe, top left, and her daughters, Melissa, 20, right, and Ashley, 17, front, were conceived using frozen embryos. In one study, led by researchers at a single clinic in Vietnam, 36% of the women implanted with frozen embryos became pregnant, while 34% of those implanted with fresh embryos did.

But the study suggests it may not increase the chances of a live birth compared to fresh embryos in the study population.

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. They also implanted, on average, two at a time.

Frozen vs. fresh embryos for IVF? Study finds little impact on fertility