Infamous cases such as the Californian woman who had octuplets as a result of IVF fuel the myth that fertility treatment will necessarily lead to a multiple pregnancy. But changing techniques and guidelines means the chances of having twins or triplets as a result of fertility treatment is now very much reduced compared to only a few years ago.

The myth that you will probably have twins or triplets if you have fertility treatment stems from the fact that, historically, the proportion of multiple pregnancies was very much higher for couples who had been through fertility treatment than for those who conceived naturally. For example, as recently as 2008, a quarter of all births achieved as a result of IVF were of twins – or more. The reason was simple: the more embryos you transfer to the woman during treatment, the higher the chance of success – which can be very attractive for someone who has endured years of infertility. But, of course, the more embryos you transfer, the higher the chances of a multiple pregnancy.

Multiple pregnancies present additional risks for both mother and baby, therefore the Human Fertilisation and Embryology Authority set targets for clinics to reduce the proportion of multiple births from 2009. Initially the target was 24% of total births, and this was then reduced further to just 10% of all live births.

Fortunately, improved techniques means we have been able to maintain success rates, while reducing the number of embryos that we transfer. The HFEA reported in 2015 that there had been a marked shift nationally from double embryo transfer (DET) to an elective single embryo transfer (eSET), with the multiple birth rates dropping from one in four IVF live births to one in six by 2013.

“We will always do what is in our patients’ interests and will give them the greatest chance of becoming pregnant,”

explains Carole Gilling-Smith, Consultant Gynaecologist and Medical Director at the Agora Gynaecology & Fertility Centre, which provides fertility expertise for people across the South East of England.

“The vast majority of our patients have a day 5 transfer (at this stage the embryo is called a blastocyst), when we know far more about the embryos than on day 3. The poorer embryos will have stopped growing and we are left with the best, which have the highest potential to implant.

“For women under 40 in their first attempt at treatment, we electively select one top blastocyst for transfer and freeze any remaining top-quality blastocysts. Our results show that we achieve no improvement in pregnancy rate by transferring two blastocyst, but increase significantly the risk of multiple pregnancy to over 40% in some cases. Our aim at the Agora is to keep our multiple pregnancy rates to well below 15%, in keeping with the HFEA multiple birth minimisation strategy.

“Another benefit of the single blastocyst transfer approach is that patients have a higher chance of embryo freezing, so overall their chances of successful outcome from one egg collection cycle is significantly higher than if two embryos had been replaced. We use a range of techniques to improve success rates including, most recently, the use of the EmbryoScope, a specialised incubator that takes time-lapse pictures of the developing embryos to help us identify those with the highest chance of leading to a live birth.”