Female twins are up to five times more likely to be affected by premature ovarian failure (early menopause) than other women, say US scientists. The researchers, who presented their findings at the annual meeting of the American Society for Reproductive Medicine (ASRM) in Montreal last week, studied 1,700 women born in the UK, US and Australia. Team leader Roger Gosden, of Cornell University in New York, said the results show that influences felt long before a women is born can affect her health and fertility in adulthood.
Premature ovarian failure, in which the menopause occurs before the age of 40, affects around one per cent of women. However, this figure rose to five per cent for the twins in the study. And by the age of 45, more than 15 per cent of twins had gone through the menopause, compared to five per cent of the general population.
Since the rate of premature menopause was similar in both identical and non-identical twins, the scientists think that the risk is not simply down to genes. It could be that sharing a womb leads to changes in the way genes are switched on and off during development. In identical twins, it is possible that the way the embryo splits during the twinning process could leave one twin with more 'egg-forming' tissue than the other. 'Our preferred hypothesis is an epigenetic one; that is not the genes themselves, but changes in the chemical groups that are stuck on to DNA and control genes by switching them on and off', said Gosden.
The study began following the case of Stephanie Yarber, an American woman who underwent the menopause when she was 13. She gave birth after receiving an ovary transplant at the age of 25 from her identical twin sister, who had normal fertility. The team that treated Ms Yarber were subsequently contacted by three sets of identical twins in the same position, who are all now undergoing treatment. This caused team leader Sherman Silber and Professor Gosden to wonder if being a twin somehow increased the risk of premature menopause.
Commenting on the study, Richard Kennedy, of the British Fertility Society, told the Times newspaper: 'We have to ask whether we should be offering screening for ovarian function at an earlier stage in twins and advising on fertility preservation measures'. Dr Margaret Rees, editor in chief of the journal of the British Menopause Society, said the research was interesting, 'but not the whole story'. She told the BBC news website that other factors could affect the age of menopause, such as smoking.