This paper uses longitudinal data (the Indonesian Family Life Survey) to study the persistent effects of in utero exposure to Ramadan over the life cycle. The exposed children have lower birth weights, study fewer hours during elementary school, do more child labor, score 7.8 percent lower on cognitive tests and 5.9 percent lower on math test scores. As adults, the exposed children work 4.5 percent fewer hours and are more likely to be self-employed. Estimates are robust to the inclusion of biological sibling fixed effects. Moreover, results are strongest for religious Muslim families, while insignificant for non-Muslims.