What happens to child development when women delay pregnancy?

In recent decades there has been a shift towards women starting families later in high-income countries. Woman may choose to delay having children for a variety of reasons, including being in school longer, student debt loads, uncertain career opportunities, the cost of childcare, and many other more personal reasons. Advances in fertility technology are also making later childbirth a more viable option for women.

It is important to understand the relationship between maternal age at childbirth and later child development because a woman’s childbearing age is related to biological, social, economic, and behavioural factors that may impact a child’s development.

Research Summary

  • Children born to the youngest mothers had the highest risk of developmental vulnerability.
  • The risk of developmental vulnerability declined with increasing maternal age up to 30 years.
  • Older motherhood was associated with a small increased risk of developmental vulnerability, equivalent to the risk for children born to mothers in their early twenties.
  • The increased risk of developmental vulnerability associated with young motherhood was largely explained by socioeconomic disadvantage.

What is the research about?

Although there is a lot of research on the increased perinatal risks of childbearing at both younger and older maternal ages, little is known about child development across the full maternal age range. The few studies that have looked at child development across the full maternal age range have lacked the sample size to be relevant to policy development.

By using data from the Australian Early Development Census (AEDC), researchers are able to examine a child’s risk of developmental vulnerability based on their mother’s age at childbirth. Whereas other studies could examine this question in 10s of thousands of children, by using a population-level database researchers from the University of New South Wales could look at nearly 100,000 children.

What did the researchers do?

The group of researchers used linked, population-level data to study the association between maternal age at childbirth and developmental vulnerability at age five for 99,530 children.

To better understand the influence of maternal age the researchers accounted for a variety of demographic factors, including:

  • child’s age at the start of the school year
  • child’s sex
  • mother partnered/single parent at child’s birth
  • mother born in Australia or overseas
  • private health insurance/patient at child’s birth
  • number of previous pregnancies
  • prenatal care before 20 weeks gestation
  • smoking during pregnancy
  • whether child speaks English as a second language
  • child’s Aboriginality
  • AEDC year
  • mother’s highest level of school education
  • highest occupation level of either parent
  • geographical remoteness
  • area-level socioeconomic disadvantage

What did the researchers find?

The average maternal age at childbirth was 29.6 years. 4.4% of children were born to teenage mothers and 20.1% were born to mothers 35 and older.

Age of motherhood mattered to child outcomes: 40% of children born to mothers 15 or younger were developmentally vulnerable, compared to only 17-18% of children born to mothers 30-35.

Overall, the risk of a child being developmentally vulnerable decreases as maternal age increases, until a certain point. Once a mother becomes 35 the risk of their child being developmentally vulnerable increases with maternal age, roughly equivalent to the risk for children born to mothers in their early 20s.

Socioeconomic disadvantage explained almost half of the increased risk of developmental vulnerability associated with younger motherhood.

What does this research mean?

The small increase in risk of developmental vulnerability for children born to mothers 35 and older is very relevant as women in many parts of the world are choosing to have children at older ages. Although socioeconomic and other advantages of older motherhood may offset biological disadvantages during pregnancy and childbirth for these women, it is important to know what is causing the elevated risk of developmental vulnerability in order to develop policies and interventions to help promote positive child development.