IVF test could predict best time for implantation

A team of Spanish researchers has developed a test that could improve IVF success rates by identifying the optimal timing for embryo transfer.

Over 60,000 IVF cycles take place per year in the UK. However, a major cause of unsuccessful cycles is implantation failure - when the embryo fails to attach into the womb lining.

Professor Juan Garcia-Velasco, of the IVI Clinic Madrid, told the Guardian: 'We think that about 15 percent of cases of implantation failure are simply due to bad timing'.

During their cycles, most women have a two-to-four-day 'window of receptivity' when the womb lining allows the embryo to attach. It had previously been assumed that this window is constant in all women. However, recent work has shown that the fertile window varies between individuals and is more likely to be displaced by a few days in women with repeated implantation failure.

In the new test a small biopsy of the endometrium is taken and the activity of 238 key genes involved in the attachment process is measured. This allows scientists to identify the patient's own window of receptivity and their optimal timing for embryo transfer.

In a pilot study seventeen women with recurrent implantation failure were given the test. Nine of these went on to became pregnant and have healthy babies.

Professor Garcia-Velasco's group is now leading an international clinical trial of the test with 2,500 patients who have had experienced recurrent implantation failure.

Up until recently research has focussed on determining the best embryo to transfer and the timing of the transfer has received comparatively little attention. Nick Macklon, professor of obstetrics and gynaecology at the University of Southampton, believes that this could explain why IVF success rates have plateaued in recent years. 'Doing these tests could significantly improve success rates,' he told the Guardian.

Professor Garcia-Velasco said of the test: 'I think it will make a significant difference in the expectations of couples and how we can explain failures. Until now, the endometrium was kind of a black box. Now we can say this was the problem and this is what we can do about it'.

Currently the test is performed at least one month before the embryos are transferred as there are some concerns that taking the endometrium biopsy could damage the womb lining and affect the embryo's ability to implant. However, the researchers are hoping to develop a less invasive version of the test that relies on sampling endometrial fluid rather than having to take a biopsy.