One embryo or two? The question that needs answering before the transfer

The decision is made in a matter of minutes on the morning of the transfer, often without anyone having really prepared for it. It deserves better consideration, because it has a greater impact on the health of the pregnancy than most other choices made during the treatment journey.

What a double transfer actually changes

Transferring two embryos does increase the pregnancy rate per transfer, that is true. But when a proper comparison is made — a transfer of two fresh embryos versus a transfer of one fresh embryo followed, if necessary, by a frozen transfer — the cumulative birth rates are equivalent. So you don’t end up with more children overall: you’re simply more likely to have two children at once.

This effect is particularly pronounced with high-grade blastocysts and in women under 38, where a double transfer mainly results in twins. With egg donation, the high embryo quality makes a double transfer even riskier from this perspective.

The risks of a twin pregnancy

These risks are not merely theoretical, and they affect both the mother and the children:

• Prematurity: around 50 per cent of twins are born before 37 weeks, compared with 7 per cent of singletons. Extremely preterm birth, before 32 weeks, is around ten times more common.
• Low birth weight, with its associated neonatal complications.
• Pre-eclampsia and gestational diabetes: the risk is at least doubled.
• Caesarean section: the vast majority.
• Postpartum haemorrhage, which is more common.
• Significantly higher perinatal mortality and morbidity.

These risks increase further with maternal age, which makes double transfer particularly questionable for women over 40, even though this is precisely the age group where it is most frequently requested.

What the professional bodies recommend

Single embryo transfer is the default recommendation for women under 38 with a good-quality embryo, and is always carried out following pre-implantation genetic testing or in cases involving egg donation. The Scandinavian countries, Belgium and the Netherlands apply this widely, with twin pregnancy rates having fallen below 5 per cent without any loss of overall effectiveness.

The transfer of two embryos is considered in specific situations: advanced age with average-quality embryos, repeated failures, or a limited number of embryos with no possibility of obtaining further ones. This is a matter for discussion, not a preference.

What Greek law permits

Greek legislation is more permissive than the recommended practice: it permits the transfer of two embryos before the age of 35 — up to three from the third cycle onwards — and up to three embryos after the age of 40. In other words, a clinic may legally offer you more than what the European guidelines recommend.

This is something I always check, and a question you should ask in advance, not on the morning of the transfer: ‘What is your transfer policy, and why in my case? ’ A clinic that offers two good-grade embryos to a 34-year-old woman undergoing egg donation must be able to justify this choice on grounds other than the patient’s request.

And what if you want twins?

I hear this often, and the reason is almost always the same: the exhaustion of the journey, the fear of having to start all over again, the cost of a second cycle. These are understandable reasons. You simply need to be aware that the price is paid elsewhere — in the risk of prematurity for the children and obstetric risks for you — and that a second pregnancy from a frozen embryo costs between 900 and 1,800 euros, which is far less than the anxiety caused by a prolonged stay in the neonatal unit. Frozen embryo transfer is described here.

The real safeguard against having to start all over again is not transferring two embryos: it is having several frozen.

Frequently asked questions

Source: https://fertilitegrece.com/en/blog/single-embryo-transfer-twins/ — Triada Baloukoudis, IVF patient coordination in Greece. General information, not medical or legal advice. Printed on