Babies best had early, say scientists

Women’s biological clocks genuinely are ticking and there seems little that can be done about it. Once women pass 35 years of age, fertility declines and it becomes more difficult to conceive and carry a baby to term.

Nor does fertilisation technology offer a ready way around these biological changes, according to researchers speaking about delaying motherhood and the science of reproductive ageing at the British Science Association Festival of Science.

Women are much more likely to delay today than in the past according to figures, said Prof Judith Rankin, of the Institute of Health and Society at Newcastle. The average age of a woman having a first child in 1986 was 27.2 years but this had climbed to 29.3 years by 2008, she said. The percentage of women having children at 35-39 had risen over those years from 6.8 per cent to 17 per cent.

Prof Mary Herbert, professor of reproductive medicine at Newcastle, said eggs are primed for fertilisation but must wait for years before being needed. The integrity of the eggs declines, and the complexity of the process means there is no intervention to renew them, said Prof Herbert, originally from Limerick. Her advice was "have your babies while you still have your reproductive fitness".

However, the researchers noted that reproductive success is different for every woman.