A recently published paper of Dr Barnhart brings us a question: are we ready to stop transferring fresh embryos and transfer only frozen embryos? Of course, he is not the first one who did that question. This is something that has been heard more frequently in the last years.

The vitrification approach for freezing is a milestone in reproductive medicine. Not only radically changed the success rates of treatments with frozen eggs, but also improved the success rates with frozen embryos, both at cleavage stage and at blastocyst stage. Now that freezing is much better, we can start thinking about some other issues that could impact in our results.

The rational is that transfer of an embryo into a more “physiological environment” would result in greater pregnancy rates and potentially decrease both maternal and perinatal morbidity. As IVF is based on controlled ovarian hyper-stimulation because working with multiple eggs/embryos increases the success rates, the endometrium receives the impact of high levels of estrogens which are not good for receiving embryos to be implanted. Nowadays, some evidence shows that pregnancies where frozen embryos have been used, have less perinatal and maternal morbidity.

Therefore, some authors suggest to freeze all the embryos, always. Although there is no agreement on that, yet, most agree that freezing all the embryos when something is not “perfect” is the best option. What is something “not perfect”? When ovaries respond too much, with risk of ovarian hyper-stimulation syndrome, when progesterone increases over 1.5-1.9 ng/mL, when endometrium doesn’t look fine, are three examples of that situation.

A fourth potential situation? In repetitive implantation failure. In those cases, freezing all the embryos and transfer them a month later seem to be the best option. I have been doing that for a long time now, and I had great results (which is supported by lots of scientific studies).

In summary, freeze all if something is not perfect; transferring frozen-thawed embryos have now very good success rates.