In the process of IVF (in vitro fertilization), embryos are typically implanted in the uterus three days after fertilization. Thanks to advancements in laboratory methods, it’s now also feasible to transfer them after five days. This change was believed to enhance the likelihood of achieving a successful pregnancy. However, recent research indicates that the timing of the transfer does not affect the overall success rate of the IVF process.
In the process of IVF (in vitro fertilization), embryos are usually placed in the uterus three days following fertilization. With recent advancements in laboratory techniques, transferring them after five days has become an option as well. This was thought to improve the odds of a successful pregnancy. Yet, a study conducted by Radboud University Medical Center and Amsterdam UMC reveals that the timing of the transfer does not impact the success rate of the entire IVF process.
In the Netherlands, one in thirty children is conceived through in vitro fertilization, abbreviated as IVF. This method involves fertilizing egg cells outside the body and cultivating them in a lab for several days. Afterwards, one or more embryos are transferred back into the uterus, while the remaining ones are cryopreserved. Traditionally, the laboratory phase spans three days, but due to technical advancements, transfer after five days is now possible. The rationale is that only embryos capable of developing are viable after five days, which is expected to boost the chances of a successful pregnancy. However, this method results in fewer embryos available for freezing.
Earlier studies indicated that the success rate was indeed higher when the first transfer was performed on day five rather than day three. However, these studies did not consider the outcomes of the entire IVF journey, particularly any further transfers of frozen embryos. The research conducted by Radboud University Medical Center, in collaboration with Amsterdam UMC, addresses this gap.
Similar success rates
The study involved over 1,200 women across 21 IVF centers in the Netherlands. At least four embryos had to be ready for transfer two days post-fertilization. Participants were divided, with one half receiving transfers on day three, while the other half had transfers on day five. The result revealed that the overall chance of achieving a successful pregnancy throughout the entire IVF process was comparable in both groups, standing at about sixty percent.
Researcher Simone Cornelisse clarifies the findings: ‘In the end, IVF is focused on achieving a successful pregnancy, not just on the probabilities following the initial transfer. In countries where IVF is not covered by insurance, clinics often promote success rates based solely on the first transfer conducted on day five, which does not provide a complete picture of the situation. Our findings indicate that women should have the autonomy to choose when their transfer occurs.’
A personal choice
Other findings from the study may affect this decision-making process. As observed in previous research, there was a greater chance of a successful pregnancy after the initial transfer on day five, along with reduced miscarriage rates within that group. Conversely, transferring embryos on day three allowed for more embryos to be frozen for future use and slightly lowered the risk of premature births. Both options have their pros and cons, but neither alters the overall success rate.
‘This is ultimately a very personal decision,’ states clinical embryologist Liliana Ramos, a lead researcher in the study. ‘For some couples, the priority might be achieving pregnancy as quickly as possible, especially if the woman is older. Others may prefer to have a greater quantity of frozen embryos or aim to minimize the risk of premature birth. Currently, there are no standardized guidelines regarding the transfer day. Thus, couples wishing to conceive should engage in discussions with their healthcare provider and make a joint decision.’
About the study publication
The findings of this study were published in the British Medical Journal under the title: Cumulative live birth rate of a blastocyst versus cleavage stage embryo transfer policy during in vitro fertilisation in women with a good prognosis: multicentre randomised controlled trial. S. Cornelisse, K. Fleischer, L. van der Westerlaken, J.P. de Bruin, C. Vergouw, C. Koks, J. Derhaag, J. Visser, J. van Echten-Arends, E. Slappendel, B. Arends, M. van der Zanden, A. van Dongen, J. Brink-van der Vlugt, M. de Hundt, M. Curfs, H. Verhoeve, M. Traas-Hofmans, Y. Wurth, P. Manger, Q. Pieterse, D. Braat, M. van Wely, L. Ramos, S. Mastenbroek.
