The health and development of children born to older mothers in the United Kingdom: observational study using longitudinal cohort data

We read with great interest the article by Sutcliffe et al. suggesting that increasing maternal age is associated with improved health and development for children up to 5 years of age. We note that among the covariates the number of siblings was included in the regression modelling. However, we are unsure after reading the manuscript whether the birth order was adequately addressed. Birth order increases with maternal age. Higher birth order is an important variable as not only does it lead to increasing maternal experience but also with greater stimulation from older siblings, which will both potentially positively impact on the outcome measures. This should be clarified as it might be the birth order rather than maternal age, which is associated with better outcomes. If this is the case then this study will be sending a misleading message to the general public.