Transferring only one embryo during in vitro fertilisation (IVF) treatment significantly reduces the risk of multiple births without considerably altering a woman's chances of conceiving and having a baby, report Swedish researchers.

In a study published in the New England Journal of Medicine, comparing single with double embryo transfer, 53 per cent of the women who had a single embryo implanted had a live baby, compared with 57 per cent of women who were implanted with two embryos.

The study involved 660 women, 330 of whom were implanted with a single fresh embryo. If that treatment cycle failed, a second embryo was implanted which had been frozen then thawed before use. The remaining 330 women were implanted with two fresh embryos.

Dr William Gibbons, the president of the American Society for Reproductive Medicine, said that these findings 'should provide comfort for those who want to perform single-embryo transfers that the pregnancy rates are equivalent'.

The study also showed that the rate of multiple births among women first implanted with a single fresh embryo was significantly lower, at just 2.3 per cent. Of the women implanted with two fresh embryos, 27.5 per cent gave birth to more than one baby.

IVF treatment has routinely involved the implantation of multiple embryos in order to increase a woman's chances of having a child, but as IVF procedures have become more advanced, doctors have been able to implant fewer embryos, with equally successful results.

However, multiple births are a common result, and incur health risks for both the mother and baby. Gestational diabetes, bleeding and pre-eclampsia, are all a risk for the mother, and the baby is at increased risk of cerebral palsy, birth defects and developmental delays.

The costs of IVF often prohibit more people choosing single embryo transfer, particularly in countries such as the US where treatment is not covered by national healthcare providers or insurance.
Moreover, 'the stress and disappointment of a failed cycle is hard to put a value on' says Dr Laurel Stadtmauer, an associate professor of obstetrics and gynecology at the Jones Institute for Reproductive Medicine in Norfolk, Virginia, US.

'This research adds further evidence confirming the value of elective single embryo transfer in assisted reproductive technologies,' said Richard Kennedy, a spokesman for the International Federation of Fertility Services.