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First born children of women in their thirties perform best in tests of mental development and psychological well-being


The firstborn children of mothers in their thirties score more highly on measures of mental development and psychological well-being than children born to other first time mothers reveals new research which will be published later this month.

According to the research(1), which is forthcoming in the December issue of the journal Biodemography and Social Biology, mothers who give birth to their first child in their thirties tend to have characteristics which help make their children perform better when measured on these outcomes at age five.

Dr Alice Goisis, a researcher at LSE, said: “First time mothers in their thirties are, for example, likely to be more educated, have higher incomes, are more likely to be in stable relationships, have healthier lifestyles, seek prenatal care earlier and have planned their pregnancies. 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 of a first child until her thirties.”

When Dr Goisis’ analysis took these social and economic factors into account, the advantages to first children born to mothers in their thirties decreased or entirely disappeared – indicating that they could be the reason for the children doing better.

However, the firstborn children of mothers in their forties do not experience the same advantages.  When assessed on their mental development and psychological well-being at age five they do significantly worse than first children born to mothers in their thirties, despite the fact that their mothers are similar socially and economically. Instead, they perform similarly to first children of mothers who give birth in their mid-twenties, albeit with an increased risk of obesity.  

Dr Goisis said: “It’s not clear why these children do less well and my findings should be treated cautiously because my sample was necessarily small, given that relatively few women have their first child after 40.

“As more women postpone giving birth to their first child, we need to look more closely at the potential trade-offs involved in terms of the mental, social and emotional well-being of the children, as well as the health implications.”

First born children of mothers aged 22 and younger do least well emotionally and in terms of their mental development.

This is the first study to look at mothers in their thirties and their forties as different groups and to have focused on firstborn children only. 

The research uses data from the Millennium Cohort Study which tracked 18,000 UK birth around the year 2000. This analysis is based on information collected when these children were around five years old (2).

Notes to Editors

(1)  ‘How are children of older mothers doing? Evidence from the United Kingdom’ is available from the LSE press office.

(2)   Children’s cognitive development was measured using the British Ability Scale Naming Vocabulary which tests the spoken vocabulary of the child - it is a validated tool to assess children’s cognitive development. Children’s behavioural and socio-economic well-being was measured using the Strengths and Differences Questionnaire, a validated tool to screen psychiatric disorders for 2-16 year olds.

Picture credit: Myles Grant   CC BY-NC-SA 2.0

Posted 19 December 2015