Women having IVF may be able to eliminate their chances of having a hazardous multiple pregnancy with a new test that can predict which embryos are likely to form identical twins.

This will allow doctors to select only embryos destined to lead to singleton pregnancies for transfer to the womb.

About one in four IVF pregnancies involves twins or triplets, who are significantly more likely to be born prematurely or underweight, or with a disability. Stillbirth and death within the first week of life are four times more common in twins and seven times more common in triplets than in singletons, while the incidence of cerebral palsy is five times higher for twins and 18 times higher for triplets. Multiple pregnancies are also much more dangerous for mothers.

Most IVF multiple conceptions are of fraternal twins, caused by implanting two or more embryos. However even if a single embryo the risk is still higher. This is a particular problem when five-day-old embryos – blastocysts – are used. These give an identical twinning rate five times higher than for natural pregnancy. The new research offers a way around this. A team led by Dianne Payne, of the Mio Fertility Clinic in Yonago, Japan, created time-lapse photographs of 33 embryos as they developed in culture, 26 of which formed blastocysts. In two of these blastocysts, the inner cell mass – the part that will go on to form the foetus – could clearly be seen to have divided into two. Had these been transferred to the womb, they would have gone on to produce identical twins.

Ms Payne said that while the results are preliminary, they suggest it should be possible to spot embryos that are developing into identical twins before they are moved to the womb.

1 in 80

Multiple births after natural conception

126

Number of deaths that would be avoided if all IVF babies were singletons

11,941

Number of babies born in multiple births in 1978

18,395

Number of babies born in multiple births in 2003

Sources: HFEA, Mio Fertility Clinic

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