FRIDAY, Aug. 7, 2020 (HealthDay News) -- Whether a frozen or fresh embryo is transferred during fertility treatments, the odds of pregnancy are roughly the same, according to a new Danish study involving nearly 500 women.
Fresh embryo transfer, however, should still be the gold standard in assisted reproduction for women, the research team said.
There was one exception to that rule, however: Women who are at risk of ovarian hyperstimulation syndrome -- a painful response to the use of excess hormones in fertility treatments.
Using only frozen embryos (a "freeze-all" strategy) during procedures such as in vitro fertilization (IVF) has become more common, noted researchers led by Sacha Stormlund, of the fertility clinic at Hvidovre University Hospital, in Copenhagen.
But the new findings "warrant caution in the indiscriminate application of a freeze-all [transfer] strategy when no apparent risk of ovarian hyperstimulation syndrome is present," the study authors concluded.
For the study, the researchers randomly selected 460 women aged 18 to 39 to receive either frozen or fresh embryos. They found that the pregnancy rates weren't significantly different between the freeze-all and the fresh transfer groups (27.8% versus 29.6%).
There were also no significant differences in the rate of loss of pregnancy between the groups and none of the women experienced severe ovarian hyperstimulation syndrome.
Also, the complication risks were not different between the groups except for higher average birth weight in the frozen group and a higher risk of prematurity in the fresh transfer group, the researchers found. The time it took to become pregnant was longer in the freeze-all group, Stormlund's group said.
Dr. Nicole Noyes directs Northwell Health's Fertility Preservation Program in New York City. Reading over the new findings, she said decisions around choosing a fresh or frozen embryo during IVF or other fertility procedures are tough, because of factors such as the unreliability of preimplantation genetic testing of embryos.
In her opinion, Noyes said, "I believe fresh [often the first candidate embryo used] transfers produce equivalent outcomes in most patient groups and involve much less perturbation of the natural embryo course."
In fact, she added, "embryo transfer of fresh embryos remains my number-one go-to in IVF today after 30 years of successfully practicing IVF in the New York City metropolitan area at three of the best clinics."
The new Danish report was published online Aug. 5 in the BMJ.
For more on IVF, head to the March of Dimes.
SOURCES: Nicole Noyes, MD, system chief for reproductive endocrinology and infertility, Northwell Health, and director, Northwell Health's Fertility Preservation Program, New York City; BMJ, news release, Aug. 5, 2020