Undergoing IVF, is fresh or frozen embryo transfer better?
Frozen embryo transfer is the process of using cryopreserved embryos which have been thawed within the IVF process and next transferred. Do statistics support any option?
Best fertility experts explain this matter in 3on1 #IVFANSWERS:
• Dr Raúl Olivares, Medical Director at Barcelona IVF
• Dr Marisa Lacárcel, Obstetrician/ Gynaecologist Eva Fertility Clinics
• Dr Maria Arquè, International Medical Director at Fertty International
Answer from Dr Olivares
Fresh and frozen embryo transfers should offer the same pregnancy rates as long as you work with blastocysts – the embryos on day 5. The new freezing technique – vitrification – has completely changed the scenario. With this technique, blastocysts have a survival rate higher than 98%. When we have problems during an egg donation cycle, for example a breakthrough bleeding or when we feel that there is a really high risk of having hyperstimulation syndrome during IVF, we don’t mind to freeze all the embryos. We know that the first cryotransfer is going to offer the patients the same success rates as the fresh embryo transfer. As we have never observed better pregnancy rates in frozen embryo transfers, we don’t share the policies of freezing all the embryos in all cycles (offered by some clinics). In our opinion, the impact of high levels of estrogens, that we sometimes get during IVF, is not enough to impair the implantation rates. We do not want to manipulate the embryos if it is not strictly necessary. As long as there is no high risk of hyperstimulation syndrome, we still carry out fresh embryo transfers in IVF with very good results.
Answer from Dr Arquè
Nowadays success rates with fresh embryos or frozen embryos are pretty much the same when we speak about blastocysts. There is emerging data saying that those are the consistent results.
Therefore, what we tend to do a lot of times is to use frozen embryos instead of fresh embryos. On the other hand, especially when we’re doing IVF with own eggs, one of the hypotheses why success rates for frozen embryo transfers are a little bit better is that all the levels of estradiol are more natural and similar to a natural cycle – even if we are doing a medicated one. That might also impact on the expression of some genes that are related with the receptivity. Therefore, we should not be afraid of using frozen embryos instead of fresh embryos because nowadays success rates in terms of pregnancies are pretty much the same. Thanks to vitrification, the technique that we use nowadays to freeze the embryos, the survival rate of the embryos (when you are working in a good lab and a good clinic) is usually more than 95-98%. It means that most of the embryos make it to the thawing process. Obviously, the criteria, that are used to decide which embryos are worth being frozen, are very strict. It maximises the chances that those embryos can survive the thawing process and give a pregnancy.
Dr Marisa Lacárcel, Eva Fertility Clinics, Spain
Answer from Dr Lacárcel
Some years ago, vitrification did not exist and the way of freezing embryos was very slow and harmful to the embryos. When we thawed them, their quality was lost or decreased. That’s why a few years ago it was better to do a fresh embryo transfer rather than a frozen one. Nowadays, with the vitrification process, things have changed. Vitrification is a fast method of freezing the embryos that maintains their quality. So when we refreeze the embryos, they are the same as if they were fresh. Thanks to vitrification, we can now transfer either fresh or frozen embryos – with the same success rates.