So far, there is no evidence that freezing all the embryos could increase the chances of success. The National Registry suggests that freezing the embryos may affect them somehow. For example, it is well-known that the birth weight is significantly higher in these embryos. This is why we usually recommend, when possible, to carry out a fresh embryo transfer, because we are not aware of these subtle changes in the embryos that the freezing and thawing process may entail.
Yes, we can’t say that all the frozen IVF cycles can be more successful than the fresh ones. It’s important to consider why we are deciding to freeze the embryos. On most occasions, we decided to freeze the embryos because of a medical reason such as the risk of a hyperstimulation syndrome in which the patient had a really high response and because of that we wanted to avoid an eventual pregnancy and we decided to freeze all the embryos to avoid future complications. A different issue is that sometimes we also decide to do what we call the preimplantation genetic screening to check the embryos, if that is the case, we need to wait for the results of that testing in the embryos and it’s advisable to freeze the embryos before transferring then as we need to wait for some days to obtain the results. So, in the past, is true that the results with the fresh embryos were much better than the result with the frozen ones. But nowadays, things have changed a lot in the laboratory and the rate with fresh and frozen could be almost the same because that is true that on many occasions we decided to freeze the embryos to do the embryo transfer at (). But in most cases, we decided to freeze the embryos for a medical reason or if we are adding additional tests such as the preimplantation genetic screening test.
