The Effect of In-Utero Conditions on Long Term Health: Evidence from the 1918 Spanish Flu Pandemic

The fetal origins hypothesis posits that in-utero stress increases the incidence of chronic conditions later in life. Utilizing 21 years of National Health Interview Survey data, this study estimates the health effect of in-utero exposure to the 1918 Spanish Flu pandemic. Exploiting the fact that people were exposed to the flu at different points during fetal development, the model tests precise predictions from the medical literature about when exposure to in utero insults should damage organs later in life. The pattern of results demonstrates the necessity of using a short duration event as a source of variation in fetal conditions and helps explain previously mixed evidence regarding the fetal origins hypothesis.