Fresh embryo transfer vs. frozen embryo transfer. What to choose?

It is necessary to mention that both frozen and fresh transfer procedures are the same. Before frozen embryo transfer, it is necessary to thaw the embryo or embryos, and it takes approx. 30 minutes. However, it’s necessary to wait for a minimum of 2-3 hours after thawing to be sure that the embryo survives. Sometimes, we thaw the embryo one day before, if they are in lower stages, in the stage of morula (early blastocyst).

Thawing embryos 2-3 hours before the embryo transfer, preparation for cryo embryo transfer is minimum 17 days because it is necessary to grow the endometrium using progesterone. At the right time, doing the embryo transfer. So preparation takes around 17 days minimum, the embryo transfer itself takes 5-10 seconds, and the entire procedure – one hour. The difference is only in the preparation. Before fresh transfer, we have hormonal stimulation and egg collection, and there is no stimulation of ovaries and no egg collection before frozen embryo transfer. There is the preparation of endometrium before frozen embryo transfer, and it can be a natural cycle or an artificial cycle. But the procedure itself is the same.

Another important question is, we go through the IVF process, we find an excellent egg donor who goes through the screening, we take all the eggs out, fertilise them, grow embryo’s and then what? Every clinic is a little different and I think that probably, the US might be a little bit different from Europe or other countries, not good or bad but just a different style. In the US today, the embryo transfers are done with something called frozen embryo transfer meaning we do not do fresh cycles, as was done in the past. In the old days you would find an egg donor, then prepare the mother for implantation and then once the eggs were out, you would transfer them back fresh. We do not do it today for one of the main reasons that we test embryo’s. Most clinic’s in the US test the embryo’s as we know that an egg donor can have 40 or 50 percent of the embryo’s being abnormal so we recommend testing them to make sure we have a good success rate. To test the embryo’s cryo freezing them.
The second reason is that the technology for freezing nowadays has changed so much. Around 15 years ago we were afraid of freezing embryos because the success rate was not as good. The thawing was not good and we compromised the embryo’s. Nowadays I would say that in our clinic as well as 98 percent of others, the cycle is done with frozen embryos, with the success rate being 70 to 80 percent. Technology has changed a lot and we are no longer worried about changing embryo’s.
I know this is not the topic but sometimes it is very counterintuitive if you think about something as delicate as embryo’s, are you sure there won’t be any damage and it doesn’t affect genetics and so on. We have done so many studies on this topic over the years, although counter intuitive embryo’s do very very well frozen. I would say in regular IVF cycles, not egg donation, there is even an argument that frozen embryo transfer is better because you put embryo’s back when the uterus is not stimulated with so many hormones, so there are a lot of other benefits for frozen embryo transfer. So we recommend not synchronizing the cycle.

People often wonder what to choose – embryo transfer in the cryo cycle, grow the embryos, freeze them and then gradually transfer them in the subsequent cycles? Or fresh embryo transfer, without freezing, right after the stimulation cycle when we collect the eggs. It’s a serious matter and each time, in each program, the decision should be taken individually for each patient.

In a stimulated fresh cycle with normal hormonal background, we can try to transfer 1-2 embryos. As for the stimulated cycles where progesterone rises, then, in these cases, it is preferable to freeze the embryos and then transfer them in cryo protocols.

There are other programs in our clinic called natural cycle IVF where cryo protocols are not implemented and are always carried out only with fresh embryos in the cycle when eggs are collected. Here everything happens naturally and there is no need to freeze the embryos. The cycle is natural, the hormonal background is natural and there is no need and benefit in embryo freezing and subsequent transfers. I would even say that such approaches are detrimental. And, once again, this is a very individual matter each time. The individual decision should be made by the doctor, together with the patient, per each individual patient, per each cycle and different hormonal backgrounds.