Children born to mothers in their 30s have the best chance of being the smartest in their class, according to a new study.
Women waiting until their 40s to start a family however, have a greater chance of having children who are overweight.
But the London School of Economics research also shows that children born to women aged 23-29 are less likely to be as clever as those who give birth to their first child at ages 30-39.
The study’s author, Alice Goisis, analysed 18,000 births in the UK and the age of the children’s mothers from data gathered by the Millennium Cohort Study, which has followed children through their early childhood years and plans to follow them into adulthood.
The average age of a first birth in the UK has increased from 24.5 to 28.1 since 1980.
However on analysing the results, Dr Goisis said the reasons behind them are more likely to be socio-economic.
‘Although the results are unable to support the argument that this occurs because of the health risks associated with giving birth at advanced maternal ages, they suggest that there is a need to more closely investigate the potential trade-offs involved when births are delayed toward older maternal ages,’ concludes the study, which was published in the journal Biodemography and Social Biology.
‘First-time mothers in their 30s are, for example, likely to be more educated, have higher income, and more likely to be in stable relationships, have healthier lifestyles, seek prenatal care earlier and have planned their pregnancies,’ Dr Goisis said, reported in The Times.
Her research also shows that older mothers were less likely to smoke, more likely to breastfeed, and more likely to read to their children.
‘These are the factors that are possibly helping their children to perform better, rather than there being an inherent advantage to a woman delaying the birth or a first child until her 30s’, she said.
When researchers controlled the experiment, specifically for socio-economic factors, results showed there was almost no difference between children born to women in their 20s and 30s, but when it was considered for women who gave birth to their first child in their 40s, the difference grew.
The authors of the study have warned that given the study pool only included 53 first-time mothers in their 40s, the results are not definitive.
‘A possible interpretation of this is that first time mothers aged 40 and above have less energy than younger mothers and may therefore be less likely to engage in recreational activities,’ noted the researchers.