Background In the UK in 2005 there were 10 000 births to women aged 40 years or over. This phenomenon of delaying child birth is on the increase. There is a well described literature on the antenatal risks to these mothers, but a dearth of studies on the effects on child health of being born to an older mother.
Aim We analysed four child health related outcomes in terms of maternal age, controlling for other covariates. Data from the Millennium Cohort Study and the National Evaluation of Sure Start (NESS) study were combined for these analyses. Separate analyses were performed on the 9 months old and 3 years old data.
The outcomes considered were:
Child has had accident.
Child has had hospital admission.
Child has had all immunisations.
Child's body mass index (BMI). These last two outcomes were available for 3 year olds only.
Outcomes were compared between children of mothers under/over 40.
Outcomes were modelled in terms of narrow bands of maternal age to give an overall picture of the outcome/maternal age relationship.
A linear, curvilinear, or piecewise linear final model was selected using the AIC fit criterion.
Covariates were controlled for in all cases (the exact list differed between 9 month and 3 year data).
Results We studied 510 children born to mothers aged 40 years or over at age 9 months, and 463 such children at 3 years. These were compared to the 25 000 other children. In general, increased maternal age was associated with improved health outcomes. The only exception to this was the decline in complete immunisation rates among children of older mothers. Two further possible exceptions were not statistically significant: (a) the slight increase in hospital admission rates among the children of mothers over 35 (3 year old data) and (b) a slight increase in child's BMI with maternal age.
Conclusion In this internationally unique and well powered study, in contrast to antenatal risks, older maternity confers health benefits to children, even those from socially deprived backgrounds (NESS dataset).
Sponsor Wellcome Trust.