The rise of fertility over 40

Marcus Roberts
July 15, 2016
Reproduced with Permission
Demography is Destiny

The UK's Office of National Statistics (ONS) has recently published a report which shows that the proportion of women having children over the age of 40 in England and Wales has overtaken that of teenagers. Women aged over 40 are having children at the rate of 15.2 live births per 1,000 women. This represents a trebling of the fertility rate of this age group over the past 35 years. As this New Zealand article suggests, there are many reasons why older women are having more children. First, advances in medicine and healthcare mean that it is more possible to conceive later in life (including artificially) and that, once conceived, it is more likely that the child will survive to birth. However, despite these advances, it is still less likely that a child conceived to an older mother will survive through the pregnancy to birth:

"Some of the risks associated with advanced maternal age are gestational diabetes, preeclampsia, high blood pressure and toxaemia…Dr Beverley Lawton from the Otago University Women's Health Research Centre says age is always going to be an important factor, as there is a strong link between maternal age and perinatal mortality.

The rate of stillbirths in women over the age of 40 is 15.84%, in someone 30-34 years of age the risk is much lower, at 9.9%."

The ONS report notes some other likely reasons for this increasing over-40s fertility rate, including: the greater participation of women in higher education and the labour force; the increasing importance of a career to many women; the rising costs of childbearing; labour market uncertainty and housing factors.

Not only is the rate at which older women in England and Wales are having children increasing, but their younger counterparts are having fewer babies. For those women aged under-20, there are now 14.5 births per 1,000 women - this means that for the first time in 70 years, the fertility rate for those over 40 has surpassed that of the under-20s. Not only is this because of older women having babies at a greater rate, but at the same time the under-20 rate has halved from the 1990-rate of 33 births per 1,000 women.

This means that the average age of a woman giving birth in England and Wales is now 30, exactly the same age as in New Zealand. (In the 1970s in New Zealand the average age was 25). But although the economic, societal and familial setting has changed remarkably in the west in the past few decades, biology has not kept up with those changes.

"Scientific Director for Fertility Plus, Margaret Merrilees, says fertility begins to decline as early as your late twenties, and by 37 it takes a 'nosedive.'

'A lot of people think they'll be fine. There are big differences in age that people don't think about. For fertility, being 40 or 41 is really different to being 43 or 44.'"

The ONS report also contained two other pieces of information which shows the changing make-up of English and Welsh society. First, the number of babies born to mothers who were themselves born outside the UK made up over a quarter of all births. This figured has climbed steadily since 1990 when it was 11.6 per cent. Second, the norm of children being born to a married couple has nearly disappeared. The percentage of all babies born outside of marriage or a civil partnership has increased slightly to 47.7 percent.

PS I couldn't imagine how hard it must be to get up the energy to deal with toddlers as a parent in one's 40s. I have enough trouble as it is with two boys under 4 and I'm only early 30s...