The benefits associated with being born in a later year outweigh the biological risks associated with being born to an older mother, researchers said.
The reason is that in industrialised countries educational opportunities are increasing, and people are getting healthier by the year. In other words, it pays off to be born later, they said.
Previous research suggests that the older women are when they give birth, the greater the health risks are for their children.
However, despite the risks associated with delaying childbearing, children may also benefit from mothers delaying childbearing to older ages, researchers from Max Planck Institute for Demographic Research (MPIDR) in Germany said.
Both public health and social conditions have been improving over time in many countries. From the perspective of any individual parent, delaying childbearing means having a child with a later birth year, they said.
For example, a ten-year difference in maternal age is accompanied by a decade of changes to social and environmental conditions. Taking this perspective, the new study shows that when women delay childbearing to older ages their children are healthier, taller and more highly educated.
It shows that despite the risks associated with childbearing at older ages, which are attributable to ageing of the reproductive system, these risks are either counterbalanced, or outweighed, by the positive changes to the environment in the period during which the mother delayed her childbearing.
For example, a woman born in 1950 who had a child at the age of 20 would have given birth in 1970. If that same woman had a child at 40, she would have given birth in 1990.
“Those twenty years make a huge difference,” said Mikko Myrskyla from MPIDR. A child born in 1990, for example, had a much higher probability of going to a college or university than somebody born 20 years earlier.
Researchers used data from over 1.5 million Swedish men and women born between 1960 and 1991 to examine the relationship between maternal age at the time of birth, and height, physical fitness, grades in high school and educational attainment of the children.
They found that when mothers delayed childbearing to older ages, even as old as 40 or older, they had children who were taller, had better grades in high school, and were more likely to go to university.
For example, comparing two siblings born to the same mother decades apart, on average the child born when the mother was in her early 40s spends more than a year longer in the educational system than their sibling born when the mother was in her early 20s.
“The benefits associated with being born in a later year outweigh the individual risk factors arising from being born to an older mother,” said Myrskyla.
The findings were published in the journal Population and Development Review.