The odds of having a healthy baby are similar after a fresh or frozen donor egg in vitro fertilisation (IVF) cycle, according to a large retrospective study. The study also supports the practice of single-embryo transfer during IVF to improve the likelihood of having a healthy baby.

The data were presented November 1 at the American Society for Reproductive Medicine (ASRM) annual meeting.

Existing literature suggests comparable embryo development between fresh and cryopreserved donor eggs, but data on live birth and obstetrical outcomes are limited, the study team, led by Alex Polotsky from CU Advanced Reproductive Medicine in Denver, Colorado, and Dr. Jennifer Eaton from Duke University, explain in their meeting abstract.

Using data from the Society for Assisted Reproductive Technologies-Clinical Outcomes Reporting System (SART-CORS), the researchers took a look back at nearly 30,000 IVF cycles to compare birth outcomes between fresh and frozen donor oocytes.

“Using fresh donor eggs is more expensive and labor-intensive than using frozen donor eggs. Using frozen donor eggs is relatively more recent. A lot of times patients are not sure which is the best approach for them, so that was the rationale for the study,” Dr Polotsky noted in an interview with Reuters Health.

Among 28,888 IVF cycles included in the analysis, about 19% were performed using cryopreserved oocytes and 81% with fresh oocytes. Baseline patient characteristics were similar between the two groups.

Use of fresh eggs (compared to frozen) was associated with significantly higher rates of implantation, clinical pregnancy, live birth, and multiple births.

But after adjustment for covariates, the odds of a good obstetric outcome, defined as a singleton live birth of 37 weeks’ gestation or more with a birth weight between 2,500 and 4,000 grams, were similar with frozen and fresh oocytes.

Elective single-embryo transfer doubled the odds of a good obstetric outcome and was significantly more common with frozen than fresh donor eggs (41% vs. 30%).

“It does appear that fresh donor eggs still do give you a high chance of implantation, contrary to some other reports,” said Dr Polotsky. “And perhaps, even more important,” he added, the study supports the practice of transferring just one embryo during IVF to avoid complications of multiple births.

“It is important to look above and beyond just a pregnancy. Nobody wants a pregnancy that has a bad outcome such as either miscarriage or very early premature birth. What you want is a healthy baby, so when you are looking for a healthy baby, transferring one embryo electively gives you a much better chance of a healthy baby as opposed to just a live birth,” Dr Polotsky said. “We just tried to figure out how to make sense of all the information that's available for so many cycles so we can counsel our patients and get the best possible outcome, which is a healthy baby.”

The analysis did find a higher rate of premature birth rate with fresh than with frozen eggs (31% vs. 26%) and a higher rate of low birth weight (31% vs. 25%).

This is “concerning and deserves more attention,” the researchers note in their abstract.

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