Frozen is fine, but fresher is better.
That’s the conclusion of a study that compared the use of fresh eggs for in vitro fertilization (IVF) against the frozen version of donor eggs.
The study, published today in the Journal of the American Medical Association, looked at 11,148 oocyte donation cycles. About 20 percent of those, or 2,227 donation cycles, involved use of frozen donor oocytes.
Live birth rates were 50 percent with fresh eggs versus 43 percent with the cryopreserved eggs, according to researchers.
For embryo transfers, the live birth rates with fresh eggs versus frozen eggs were 56 percent and 47 percent, respectively.
Twelve percent of those fresh oocyte initiated cycles were canceled while 8.5 percent of the frozen oocyte cycles were canceled.
“We were not surprised by the observed lower pregnancy rates with frozen eggs compared to fresh,” Dr. Vitaly A. Kushnir, Center for Human Reproduction in New York, told Healthline. “However, we were pleasantly surprised that the pregnancy rates were still quite high for both frozen and fresh eggs.”
Fresh Eggs Are the ‘Gold Standard’
For the study, Kushnir and his colleagues used data from the 2013 annual report of U.S. IVF center outcomes published by the Society for Assisted Reproductive Technology to compare live birth and cycle cancellation rates using fresh and cryopreserved donor oocytes.
The data set was based on voluntarily reported outcomes from 380 of 467 U.S.-based fertility centers, which in 2013 collectively performed 92 percent of all IVF cycles.
“Use of fresh eggs remains the gold standard since the pregnancy rates are superior and we have many years of experience and know much more about the safety of IVF with fresh eggs,” Kushnir explained. “Additionally, most patients desire more than one child. Since, in fresh donor egg cycles recipients generally get more donated eggs, they have extra embryos, which can be frozen and used to try for a sibling years later. However, donated frozen eggs may offer a compelling alternative for some patients due to immediate availability and possibly lower cost.”
In January 2013, the American Society for Reproductive Medicine declared the technique of using frozen eggs for in vitro fertilization was no longer considered experimental.
“Women who are considering electively freezing their own eggs for fertility preservation should be counseled that pregnancy chances with frozen eggs may be somewhat lower than with fresh,” Kushnir added.
Difficulties with Frozen Eggs
Kushnir said freezing eggs, while becoming a more common procedure, is difficult because they are big cells and have difficulty thawing efficiently.
He and his colleagues were skeptical that pregnancy rates with the frozen donor eggs could be as high as the fresh donors.
“Specifically we were concerned because of the technical aspects of egg freezing,” he said. “And also because most recipients of frozen eggs get only a fraction of the eggs each donor produces in frozen cycles whereas in fresh cycles the recipient usually gets all of the donated eggs.”
Typically a frozen donor receives about five or six eggs, whereas a fresh one receives more than 15.
Kushnir and the researchers also cautioned that, while all signs have been reassuring thus far, there has not been extensive research regarding long-term safety issues in children born from frozen eggs.
In addition, the researchers noted the findings should be looked at with caution because the outcomes don’t factor in donor and recipient ages, infertility diagnosis, and embryo stage.
All that said, Kushnir still believes there is a bright future for people interested in going down the IVF route. However, he said these options should be meticulously studied and examined along the way for best practices.
“The good news is that there are more reproductive options now [more] than ever, but we must proceed with caution,” he said. “IVF is evolving quickly with many new techniques and technologies [are] being introduced. It is important that before wide utilization the safety and efficacy of each be vetted in well-designed studies.”