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Fresh vs. Frozen Embryo Transfer: Which is Better for Older Patients?

Standard IVF practice has assumed that “fresh is better than frozen,” but some fertility centers are proposing that all embryos be frozen before transfer. CHR disagrees – learn why.

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Fresh versus frozen embryo transfer–

We have repeatedly addressed the question of whether it is better to transfer fresh or worse to transfer frozen embryos. We have done so because in recent years some studies have appeared in our literature which suggested that the standard IVF practice which for over 30 years has assumed fresh transfers result in better pregnancy rates should be abandoned in favor of “all-freezes” (meaning freezing all embryos and then transferring them subsequently in a cycle that is not exposed to fertility drugs.

The hypothesis that our colleagues who suggested to this change in practice proposed was that those fertility drugs caused so many hormonal changes in a stimulated cycle that negatively affected the implantation process that outcomes would be better (Pregnancy rates would be higher) if embryos were first frozen and then transferred in a subsequent cycle.

We never subscribed to this hypothesis and we extensively wrote about it because we thought that the data that the colleagues that were supporting this hypothesis was manipulated.

Interestingly, just two weeks ago, two major publications appeared in the prestigious New England Journal of Medicine–one published mostly by Chinese colleagues with some American contributions (though all the studies were performed in China), the second was performed in Vietnam. Both were large studies, which is obviously always important for statistical considerations. The larger study population, the more reliable will the results be. And both studies came to identical conclusions. And the conclusion was that there was no difference. In other words, transferring embryos fresh or transferring embryos frozen (if it’s the same embryos) has very similar outcomes.

Now, how should this data be interpreted?

One way of interpreting the data is obviously by saying that it makes no difference and that is true for the kind of patient population that those studies reported. And those were general populations. Those were not particularly old patients, those were not patients with low ovarian reserve, those were the the standard IVF patient, and they were indeed relatively young. Therefore it is very very important to understand that when we all now can agree that in principle, fresh or frozen embryos have very similar pregnancy rates, that really applies only to those kinds of populations. This does not apply to what we call “Poor Prognosis Patient.” It does not apply to women above age 40. It does not apply to women even if they’re young if they have low ovarian reserve.

Those patients need to be treated very very differently and I can tell you with virtually 100% certainty based on data that we have generated now for years here at CHR that in those patients, in those poor prognosis patients, there is a significant difference between transferring fresh embryos and transferring frozen embryos and fresh embryos clearly have better outcomes. Maybe not because they are so much better in terms of implantation potential, but embryos that come from older women or from younger women with low ovarian reserve simply don’t freeze and thaw as well as embryos from younger women.

That is an important message: that freezing and thawing in poorer prognosis patients leads to more egg and embryo loss, and I mentioning eggs because the same thing applies to egg freezing. Therefore, freezing works beautifully (especially now that our freezing technologies have so much improved) with younger and uncomplicated patients, but if you are older or if you are a poor prognosis patient because you have low ovarian reserve, the old dictum still holds: fresh is better than frozen.