British Pregnancy Advisory Service logo

11 September 2013

UK: Biological clock warnings in the news again

Most women’s fertility begins to decline sharply in their mid-thirties but a growing number are waiting until a later stage in order to focus on a career or save money, experts from Newcastle University said.

The percentage of mothers giving birth aged between 35 and 59 rose from 6 per cent in 1986 to 17 per cent in 2008, while the median age for giving birth increased from 27.2 years to 29.3 over the same period.

Women should not assume that advances in fertility treatments will allow them to delay having children until after their biological “clock strikes 12”, said Prof Mary Herbert, a specialist in reproductive biology.

Speaking before a public discussion on fertility at the British Science Festival in Newcastle, 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.”

Research shows that better-educated women are more likely to delay having a child, with climbing the career ladder and the cost of childcare two of the leading factors affecting their decision, the Daily Telegraph reports. But as women age, their chances of conceiving decline and the risk of stillbirths and conditions such as low birth weight, preterm birth and Down’s syndrome increase steadily.

The decline in fertility is generally slow in the twenties and early thirties, but increases much faster thereafter, with most women stopping childbearing in their early forties.

Judith Rankin, a professor of maternal and perinatal epidemiology at Newcastle, said women who wanted families ought to at least begin thinking about having children in their twenties.

“I think it’s better to think about it [in your twenties], and have that thought process informed by all possibilities,” she said. “From a public health perspective, when we look at the whole population, [the] message has to be that if you’re 35 or over, your likelihood of pregnancy is greatly reduced.”

Although IVF techniques can now allow women to have children later in life, their chances of success using their own eggs, rather than those of a donor, falls at the same rate as their fertility.

Natika Halil, of the Family Planning Association, said: “Conversations about planning a family are important, as is accurate information about contraceptive choice. Women are mindful of their fertility and any discussion should be done without scaremongering. Fertility doesn’t disappear after 35 and doesn’t stop overnight.”

A post on the bpas blog criticised the one -sided character of warnings about the “biological clock”. The post said:

“We are concerned that these admonitions are issued in a way that completely ignores the reality of women’s lives and the very understandable reasons why women are choosing to have children later in their thirties.

“In our experience there are many factors which lead women to delay starting their families into their thirties. Career pressures may be among them, but this is often closely related to women wanting financial security before having a baby, and indeed their own home. The importance of being in the right relationship is for many women paramount, as few want to take on the responsibility of parenthood with a partner they are unsure about.

“We also need to be wary of overstating the risks of later motherhood. If anything many women now overestimate the difficulties of getting pregnant after the age of 35 - we see many women in this age group with unplanned pregnancies after taking chances with contraception because they believed their fertility had declined dramatically. We need to work harder to understand the reasons for later motherhood and not scaremonger or stigmatise those who make the rational and considered choice to delay starting their families until they are ready.

Don’t leave babies until your thirties, women are told. Daily Telegraph, 10 September 2013

The fertility “clock strikes 12” at 35. bpas blog, 11 September 2013

tweet