2 embryos better than one for IVF success

TWO embryos are better than one for maximising the chances of having an IVF baby at any age, a study has found.

In older women, the transfer of two embryos rather than one was less likely to lead to multiple births, low birth weight or premature birth than in younger women.

Decisions about how many embryos to implant during a single in-vitro fertilisation cycle are controversial.

Some fertility clinics have been accused in the past of taking risks with women’s health by implanting multiple embryos to increase the chances of a live birth.

The Human Fertilisation and Embryology Authority (HFEA) which regulates IVF clinics in Britain, has issued guidance that generally no more than one embryo should be implanted per cycle.

Older women or those with poor quality embryos are considered exceptions to the rule who may be suitable for double embryo transfers.

The new research found that three or more embryos should not be implanted at any age because of the risks involved. However, it was less clear cut about the question of transferring one or two embryos.

Authors Professor Debbie Lawlor, from the University of Bristol, and Professor Scott Nelson, from the University of Glasgow, said clinicians and patients should be given “greater freedom” to decide whether one or two embryos was the right number to use.

The study analysed the outcomes of 124,148 IVF cycles resulting in 33,514 live births.

Rates of live birth, multiple births, and premature birth were compared in women younger than 40 and those aged 40 and over.

In both age groups, live birth rate was greater with the transfer of two embryos than with one, while older women were less likely to encounter adverse outcomes.

The researchers wrote: “We found that the number of embryos successfully fertilised affected the outcomes, so that in a younger woman with only two or a small number of embryos successfully fertilised there may be a case for transferring two, rather than just one (as legislated in some countries currently).

“In view of these findings and previous findings, we conclude that no more than two embryos should be transferred into women of any age, but greater freedom should be given to clinicians and patients to decide whether to transfer one or two embryos, according to prognostic indicators, such as maternal age.”

Implanting three or more embryos was risky for women of any age and did not significantly increase the chances of giving birth to a live baby.

The findings highlighted the importance of the role age played in IVF success.

“Couples need to understand that delaying childbirth until older ages of the mother may make it difficult to conceive and harder for IVF to be successful.”