Should we transfer only one embryo? Is more better?
Both single and multiple embryo transfers come with potential risks and advantages. What are the benefits and risks of single embryo transfer? This question is answered by our experts in 3on1 #IVFANSWERS:
• Dr Marisa Lacárcel, Obstetrician/ Gynaecologist Eva Fertility Clinics
• Dr Raúl Olivares, Medical Director at Barcelona IVF
• Dr Maria Arquè, International Medical Director at Fertty International
Dr Marisa Lacárcel, Eva Fertility Clinics, Spain
Answer from Dr Lacárcel
In assisted reproduction, we believe it is better to have a pregnancy with only one baby. If we have twins, we have more possibilities of some problems, like hypertension and diabetes in the pregnancy or premature delivery. So we believe it is better to do a single embryo transfer if we have embryos with high quality.
Answer from Dr Olivares
I can’t really see any advantage of transferring more than one embryo, other than shortening the time to pregnancy – obviously at the risk of that being a twin pregnancy. I think our role as the fertility doctors is not just trying to get a pregnancy at any cost. We have to focus on maximising the chances of obtaining healthy babies. And the easiest way of doing that is having single pregnancies. This is why one of our general policies is to carry out single embryo transfers in all egg donation cycles in which the quality of the embryos is going to be good and in all the IVF cycles in which we are transferring genetically normal embryos to patients who have pre- implantation genetic screening done. On top of that, we know that the embryos do not interact with each other when we transfer them together: they don’t help each other, they don’t disturb each other. It means that if you transfer two embryos, you are going to have higher pregnancy rates in that transfer – but the overall pregnancy rate of the cycle, the so-called ‘cumulative pregnancy rate’, is going to be exactly the same. The only drawback of transferring one embryo each time is that you may need more attempts to reach that overall pregnancy rate. But it is not going to change at all. So we have to balance very well the risks involved in transferring two embryos and recommend a single embryo transfer whenever we can.
Answer from Dr Arquè
After several years of experience in the field of reproductive medicine, there has been a change in the tendency of the number of embryos that we transfer. Nowadays the global tendency is to transfer one single embryo. Especially when we are transferring the embryos at the stage of blastocysts, the quality of the embryo is usually good. Therefore, the likelihood of a pregnancy is good as well. One of the most important things that we have to remember, when we’re doing fertility treatment, is that our role is not only to get a patient pregnant but also to make sure that she has a safe pregnancy – and that she and the baby are healthy along the pregnancy and that its outcome is good as well. We know for sure that twin pregnancies and multiple pregnancies are much more risky than singleton pregnancies from the obstetrical perspective. There is a much higher risk of preeclampsia, gestational diabetes, pre-term delivery and other obstetrical complications along the pregnancy. Therefore, the single embryo transfer would be the recommended kind of transfer. Nevertheless, there are some specific cases in which we may consider transferring two embryos, especially in cases when we have had several failures before or when we know that the quality of the embryos is not the best. But generally, to reduce as much as possible the risks of complications along the pregnancy and maximise the chance of having a healthy baby, a single embryo transfer would be advised.