Chance of success with single embryo transfer
For in vitro fertilisation (IVF) patients, the risks to the mother and child involved in multiple pregnancy and birth are caused by transferring 2 or more embryos (see Risks to the mother and Risks to the child).
It would be much better for mothers and children if multiple births after IVF could be made less likely, but without significantly affecting the chance of becoming pregnant. The good news is that this is possible.
If you are young, healthy and have a good chance of conceiving after IVF, you are at greatest risk of a multiple pregnancy. Opting for single embryo transfer (SET), where only 1 embryo is selected for transfer, dramatically reduces your risk of a multiple birth, while your chances of becoming pregnant remain good.
The expert says...
"International data shows that the incidence of twins after IVF can be reduced without damaging women’s chances of conceiving."
Professor Peter Braude, Chair, Expert Group on Multiple Births after IVF, Head of the Department of Women’s Health, King’s College London
Who is most suitable for single embryo transfer?
Evidence from the medical literature suggests that the use of single blastocyst transfer does not reduce your chance of becoming pregnant by IVF, but will reduce your risk of having a twin pregnancy if:
- you are under 37.
- you are undergoing your first or second IVF treatment (that is, you don’t have an extended history of failed IVF attempts).
- you are able to produce at least 3 good quality embryos on day 3.
Other factors can affect your chances of a successful pregnancy, for example: embryo quality, endometriosis, tubal disease or whether you have been pregnant with IVF before.
SET is not suitable for everyone, so you should always discuss your options with your clinician.
Did you know?
In Sweden, 70% of all IVF cycles are now elective single embryo transfer (eSET) cycles. The twin rate has reduced from over 20% to around 5% but overall pregnancy rates have been maintained – it is still ranked 4th for live birth rates.
Won´t single embryo transfer halve my chance of getting pregnant?
It seems the opposite of what you'd think, but data from countries that have already used SET more widely shows that your chances of becoming pregnant are comparable with those where multiple embryo transfer is used. The factors that make this possible are:
- you are a suitable patient (that is, you are under 35, with a good chance of conception with IVF).
- the best quality embryo is selected for transfer.
- 5 to 6 day embryo (blastocyst) transfer is used where possible.(See Embryo transfer: 5 - 6 days.)
- other good quality embryos you may have produced are frozen for use in further treatment if necessary.
In these circumstances, your chances of becoming pregnant are similar to those where multiple embryo transfer is used, but with SET, the risk of having a multiple pregnancy and birth and its consequent problems, are greatly reduced.
What are the disadvantages of single embryo transfer?
At present, SET is not a perfect solution to all the problems of multiple pregnancy and birth. If your first fresh embryo fails to implant, you will have to go through further IVF treatment with frozen embryos, making your treatment last longer and possibly cost more. However, it by no means doubles the cost or halves your chance of becoming pregnant.
