Research says children of older mothers are smarter, taller, and stronger

There are benefits to waiting.
There are benefits to waiting.
Image: Reuters/Lucas Jackson
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The risks of having children later in life are well documented: there’s a higher chance the baby will have issues at birth, like Down’s syndrome, or be more likely to develop autism and Alzheimer’s later in life. It’s also simply harder to get pregnant as time marches on.

But a study of more than 1.5 million Swedes shows there are some pretty big benefits as well.

Kids born to older mothers are taller, less likely to quit school, more likely to attend university, and tend to perform better on standardized tests than siblings who were born before them.

More fodder for the frenzied debate about birth order.

Consider a woman born in 1960 who has one baby when she is 20 and another when she is 40. A lot of things happened in those intervening 20 years, including dramatic improvements in medicine, mortality, and education: the kid born in 2000 is much more likely to go to college than the sibling born in 1980.

Women around the world are postponing having kids to later for reasons ranging from better access to birth control, improved professional opportunities, and rising economic uncertainty.

In 1968, about 75% percent of all births in Sweden were to mothers younger than 30. By 2013, roughly 60% of births were to mothers aged 30 or older.

Mikko Myrskylä of the Max Planck Institute for Demographic Research and Kieron Barclay of the London School of Economics collected data from more than 1.5 million Swedes born between 1960 and 1991. They looked at siblings (excluding twins and other multiples) and examined the relationship between a mother’s age when she had her kids, and certain attributes of those children, including height, physical fitness, grades in high school, and educational attainment.

Their study was published this week in the Population and Development Review.

Sweden is at outlier in some respects—education is free at all levels, and as a result the rate at which people attend post-secondary school is higher than the OECD average. Between the 1960s and 2000s, tertiary education enrollment increased substantially; in 2012, about 33% of Swedes had completed post-secondary education, according to the study.

But the trends are similar elsewhere: US and British children are also pursuing more education, and mothers are having babies later there too. And while the researchers can’t recommend waiting longer to have kids—the risks are very real, with about one in 200 babies born to women aged 40 or older having Down’s syndrome compared with one in 1,500 born to mums aged 20 to 24, for example—they conclude that in the population they studied, the benefits outweighed the costs.

“We show that the macro-level trends outweigh the individual-level risk factors,” they write, referring to postponing childbirth until 40.

The study adds to the well-known benefits to becoming a parent later down the road: older mothers tend to have advanced in their careers more, which gives them more life experience and earnings power.

“We need to develop a different perspective on advanced maternal age,” Myrskylä says. “Expectant parents are typically well aware of the risks associated with late pregnancy, but they are less aware of the positive effects.”