Abstract: A large literature has linked the in utero environment to health in adulthood. We consider how prenatal nutrition may shape human capital acquisition in childhood, utilizing the month-long Ramadan fast as a natural experiment. In student register data for Pakistani and Bangladeshi families in England, we examine whether Ramadanīs overlap with pregnancy affects subsequent academic outcomes at age 7. We find that test scores are 0.05 to 0.08 standard deviations lower for students exposed to Ramadan in early pregnancy. Our results suggest that brief prenatal investments may be more cost-effective than traditional educational interventions in improving academic performance. Download this paper.