Pregnancy less successful with two embryo IVF

New research has claimed that implanting two embryos during IVF can cut the chances of becoming pregnant by more than a quarter if one of the embryos is in a poorer state of health.

Being presented at the British Fertility Society annual conference, the study examined almost 1,500 embryos that were implanted in women of all ages, discovering that putting back a healthier embryo alongside one of poorer quality was a large influence in cutting the chance of a successful pregnancy when compared to transferring just one embryo.

The data, involving 1,472 fresh single and double embryo transfers on day five after fertilisation, suggested that the female body focuses on the ‘poorer quality’ embryo and rejects a possible pregnancy, rather than focusing on the healthy embryo that would lead to a successful birth.

The transfers, which were carried out between between June 2009 and December 2013 at the Nurture Fertility clinic in Nottingham, showed that transferring two embryos where one was good quality and one was poor resulted in a 27 per cent lower chance of achieving a pregnancy.

The researchers have recommended that women of all ages with a good embryo should just have one embryo put back in their body during IVF, including older women. The second embryo could then be frozen for future transfer.

In contrast to this, the research also suggested that for women who possess two poorer quality embryos, the chances of falling pregnant are higher with two transfers than just with one.

Nick Raine-Fenning, medical director and research lead at Nurture Fertility, said: “The current feeling is that a good embryo will be recognised by the body and will be captured for implantation. But a poor quality embryo should be rejected by your body, your endometrium will reject it. What our research suggests is that if you put a poorer quality embryo back with a good one, it’s more likely to compromise the chance of the good one implanting.

“This research shows the importance of quality over quantity. It helps better guide the contribution and risk when considering replacing a second embryo. Most patients understandably expect adding a second embryo will increase or even double their chances but this has never been the case.”

The Human Fertilisation and Embryology Authority (HFEA) encourages women of the benefits of having embryos transferred one at a time during IVF.