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11 April, 2018

Fertility. The final decision on #embryo transfer: How many embryos do I transfer? One or two?

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Rafa and Susana are going to start their assisted reproduction treatment at HC Fertility. And they have to make the final decision of the embryo transfer. We ask them:

How many embryos do you want to transfer, one or two?

It seems incredible to be at this point and they have not yet made a final decision. At the beginning of the treatment, we discussed with them the good prognosis to achieve pregnancy and the possibility of transferring a single embryo and vitrifying the rest.

But the couple thinks of the over two years they have been trying for a pregnancy without success, before coming to our clinic. With the intense desire to be parents, most of their friends with a partner already have children.

They weigh the economic and emotional effort that it has been getting here. They already know what it is to face a negative beta-wait (time that elapses between the last step of the assisted reproduction treatment – artificial insemination or IVF, and the time to do the pregnancy test), since they underwent two Artificial Inseminations before passing to In Vitro Fertilization. For work and personal situations they both prefer a single pregnancy and later seek a second pregnancy, although transferring two embryos increase the chances of getting pregnant. It comes to mind the double baby carts that are increasingly seen, even remember a couple of friends who had triplets that were in neonatal for a while.

Despite our technical recommendations, like most couples in Spain, they finally decide to transfer two embryos to the uterus.


Who decides how many embryos are transferred?

Specialists have the obligation to adequately inform both the risks that can lead to multiple pregnancy and the chances of pregnancy with a single embryo. When we talk about transferring a single embryo, we refer to a blastocyst transfer, embryo on day 5 or 6 of culture.

But the patients decide. The autonomy of the couple or of the woman alone to decide the number of embryos to transfer is indisputable.


What is the situation in Spain?

According to the 2014 data of the Spanish Fertility Society, the average number of embryos transferred in Spanish clinics was 1.8 embryos per transfer.

Specifically, in IVF treatments with own oocytes where it was possible to choose embryos to transfer, 8 out of 10 transfers were of two embryos, and only 2 out of 10 were from a single embryo. In these cases, the gestation rate for each transfer of two embryos is 41%, and 1 in 4 of these pregnancies is twin.

Until recently, the transfer of two embryos has been the most common practice in our country, but each day it tends more to long culture on day 5 or 6, that is, blastocyst stage, and single embryo transfer. Although there was no legal limit in the past, Spanish law currently allows a maximum of three embryos to be transferred.


Pros and cons of transferring two embryos.

Technological advances along with a greater scientific knowledge over the last decade have made possible an increase of pregnancy rates in assisted reproduction.

It is also true that it has been associated with an increase in multiple pregnancies, which are considered risky for both the mother and the babies.

Today the main risks in pregnancy for professionals who work in reproduction are multiple gestations, along with the increase in gestational age in women.


Future trend: a single embryo?

The consensus trend among experts is to reduce the number of embryos transferred, and reduce the risk of multiple pregnancies. The improvement of embryonic culture in recent years has allowed embryos to be taken to day 5 or 6 of culture, selecting the best embryo at the blastocyst stage. International scientific societies such as the European Society of Human Reproduction (ESHRE) consider that the real success in an assisted reproduction treatment is the transfer of a single embryo and a healthy child at home. More and more European countries are carrying out this recommendation, being mandatory in countries such as Belgium or Sweden the transfer of one embryo to couples with a good prognosis.

It is necessary to explain that with the transfer of a single embryo (SET, Single Embryo Transfer in English) the pregnancy rate per transfer decreases, but in the whole cycle there is not so much cumulative difference, because the embryos of good quality that are not transferred are vitrified and saved to be transferred at a later date.

Spain is a very advanced country in assisted reproduction techniques, and is at the international head in success results, so the transfer of a single embryo in blastocyst stage has been the recommendation to couples with a good prognosis and the trend of the future.

At HC Fertility we are in the technical vanguard and we have a team of professionals with a lot of experience and very good results, who study each case in a personalized way to advise patients with the decision of the number of embryos to transfer taking into account the probabilities of pregnancy and the risks of multiple pregnancy.

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