Radboud University Medical Center, A new study from Radboud University Medical Center and Amsterdam UMC has revealed that the timing of embryo transfer during in vitro fertilization (IVF) does not significantly impact the overall success rates of the procedure. Traditionally, embryos are transferred to the uterus three days after fertilization, but advancements in laboratory techniques now allow for transfers to occur five days post-fertilization.
In the Netherlands, approximately one in thirty children is conceived through IVF, a process in which egg cells are fertilized outside the body and cultivated in a lab before one or more viable embryos are implanted in the uterus. While the conventional approach has been to perform the transfer at three days, the five-day method is based on the belief that only the most viable embryos remain at that time, potentially increasing the chances of a successful pregnancy. However, this approach results in fewer embryos available for freezing.
Previous studies indicated a higher success rate for pregnancies initiated with a five-day transfer compared to a three-day transfer, but they did not consider the entire IVF process, including subsequent transfers of frozen embryos. The recent research addresses this gap.
Conducted across 21 IVF centers in the Netherlands and involving over 1,200 women, the study required participants to have at least four embryos available for transfer two days post-fertilization. The women were divided into two groups: one underwent embryo transfer on day three, while the other on day five. The results showed that the overall chance of achieving a successful pregnancy was approximately 60% in both groups.
Researcher Simone Cornelisse emphasized the importance of considering the entire IVF journey, stating, “Ultimately, IVF is about achieving a successful pregnancy, not just the chances after the first transfer. In countries where IVF is not covered by insurance, clinics often highlight their success rates based solely on first transfers on day five, which can mislead patients. Our study indicates that women should have the freedom to choose when to have their embryos transferred.”
The study also highlighted additional factors that may influence this decision. Consistent with earlier findings, women who had their first transfer on day five experienced a higher likelihood of successful pregnancies and fewer miscarriages. Conversely, those opting for a three-day transfer had the advantage of being able to freeze more embryos for future use and faced a slightly lower risk of premature birth. While both options present their own benefits and drawbacks, they do not affect the overall success rate of the IVF process.
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