While delaying pregnancy is often associated with risks for the foetus, a team of scientists now claim that children born to older mothers tend to be healthier and more educated.
For the past three decades, the mean age of mothers at first birth has increased across the OECD countries, at a rate of 0.08 years annually. This average age is now 30 in most countries, including the UK.
This trend has a number of negative consequences. Many studies have, for example, linked advanced maternal age (often defined as 40 years old and above) to a range of negative health outcomes, such as pregnancy complications, Down's syndrome, autism or even childhood cancer.
This latest research, published in Population And Development Review, argues that while these risks are real, most studies forget to acknowledge that progresses are being made every day in the health and education field to reduce them. The authors say being born later could have a range of ignored health and socio-economic benefits, which they sought to identify.
Height, fitness and general health
The team analysed data from over 1.5 million Swedish men and women born between 1960 and 1991. The scientists specifically looked at the relationship between time of birth and physical fitness and height, two good proxys for general health.
They found an association between delaying childbirth, even to ages as old as 40, and having taller and healthier children. For example, they discovered that "individuals born to teenage mothers are 1.3cm shorter than those born to mothers aged 25–29, while those born to mothers aged 40–44 are 0.4cm shorter".
Children of mothers who delay pregnancy also tend to spend more time in education. The scientists found that the highest mean number of years in education was among individuals born to mothers aged 30–34, with 13.1 years spent in school.
More importantly, they compared siblings in the same families, born decades apart. This method contributed to the credibility of their results. "By comparing siblings who grew up in the same family it was possible for us to pinpoint the importance of maternal age at the time of birth independent of the influence of other factors that might bias the results," says co-author Kieron Barclay.
On average, the child born when the mother was in her early forties spent more than a year longer in the educational system than a brother or sister born when the mother was in her early twenties.
Though what they report are only correlations, the scientists have looked at a wide range of data, and believe the results are robust enough to change perceptions regarding late pregnancies.
"The benefits associated with being born in a later year outweigh the individual risk factors arising from being born to an older mother. We need to develop a different perspective on advanced maternal age. Expectant parents are typically well aware of the risks associated with late pregnancy, but they are less aware of the positive effects," concludes co-author Mikko Myrskylä.