Women should have babies before the age of 35, says one of Britain’s top experts on reproductive ageing.
That is when the “clock strikes 12” and the chances of motherhood are cut by chromosomal damage no amount of fertility treatment can reverse, argues Professor Mary Herbert.
Too many women fail to understand the hard reality that their reproductive time runs out relatively early in life, she maintains.
The professor, from the Institute for Ageing and Health at the University of Newcastle, spelled out her message at the British Science Festival.
Explaining the chromosomal abnormalities that appear in an older woman’s eggs, she said: “What we can say for sure is that reproductive technologies do not do much to buy time.
“Perhaps the most important message to give is that the best cure of all is to have your babies before this clock strikes 12.
“I would be getting worried about my daughter if she hadn’t had a child by 35.”
She and other experts speaking at the festival, held at the University of Newcastle, stressed that family planning should involve thinking about the timing of pregnancy as well as contraception.
Women are born with a pool of one to two million eggs that decrease in number until at the menopause they effectively run out.
But it is not only the number but the quality of eggs that is reduced by the passing years.
Over time, a woman’s eggs can end up with too many or too few chromosomes - the strands of packaged DNA that contain our genes.
The chromosomal abnormalities lead to infertility, stillbirth, or birth defects such as Down’s syndrome.
Sadly, there is no practical solution to this problem, the experts point out.
Even freezing eggs for future use, a technique still in the early stages of development, could not guarantee success and was prohibitively expensive.
Yet women were increasingly delaying motherhood. Between 1986 and 2008 the typical age at which a British woman had children rose from about 27 to 29. Over the same time period, the proportion of mothers aged 35 to 39 rose from 6.8% to 17%.
“Women tell me it’s their career,” said Professor Herbert. “In a sense I think that’s misguided, because there’s no career where it gets less busy as you go on.”
She thought it was something society needed to address as well as individual women, who were not being properly informed.
“I think it goes beyond the message to women,” she said. “It goes to the message to policy makers. We need to understand what the barriers are to women having their children early.”
Colleague Professor Judith Rankin, from the Institute of Health and Society at the University of Newcastle, said: “The big message from where I’m coming from is I don’t think women understand the risks there may possibly be when they reach older ages.
“There is quite good evidence about some of these outcomes and for me the whole driver for ante-natal care in this country is about informed choice.
“How can women make an informed choice if they’re not being told the risks and told that side of the story?”
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