Mothers' school starting age and infant health

We study the effects of women's school starting age on the infant health of their offspring. In Spain, children born in December start school a year earlier than those born the following January, despite being essentially the same age. We follow a regression discontinuity design to compare the health at birth of the children of women born in January versus the previous December, using administrative, population‐level data. We find small and insignificant effects on average weight at birth, but, compared to the children of December‐born mothers, the children of January‐born mothers are more likely to have very low birthweight. We then show that January‐born women have the same educational attainment and the same partnership dynamics as December‐born women. However, they finish school later and are (several months) older when they have their first child. Our results suggest that maternal age is a plausible mechanism behind our estimated impacts of school starting age on infant health.