The Long-Run Effects of Cesarean Sections

Cesarean section is the most common surgical procedure in many countries around the world. Numerous recent studies have shown an association between cesarean section and several adverse outcomes for the mother and the child. However, there is a lack of knowledge regarding the causal nature of this relationship. In this paper, we try to help fill this research gap by providing credible causal evidence of the long run effects of cesarean sections on policy relevant health outcomes using large and precise administrative data registers. To do so, we use exogenous variation in the probability of having an unplanned cesarean birth. We show that physicians are more likely to perform C-sections during their regular shift on Fridays and working days that precede public holidays and use this variation as an instrument for unplanned C-sections. We complement these results using variation within and between sibling pairs: we compare the health gap between the second and the first child in families where the second child is born by unplanned C-section with respect to families where both children were born by vaginal delivery.

We investigate the effects of cesarean sections on infant outcomes using a rich data resource which includes birth and health records for all children born in Finland between 1990 and 2014. We follow entire birth cohorts from birth to teenage years and use detailed diagnosis data to study the causal effects of cesarean sections on child health. We focus on the outcomes whose onset is hypothesized to be influenced by cesarean delivery: asthma and other atopic diseases, type 1 diabetes, and obesity. Understanding and quantifying the potential contribution of C-sections to the development of these diseases is important, given their high direct and indirect costs.

Our instrumental variable estimates suggest that avoidable C-sections increase the probability of an asthma diagnosis from early childhood onwards. This effect is of clinical and economic relevance, and consistent with the hypothesis that mode of delivery can impact the development of the immune system. However, we do not find consistent evidence that cesarean sections affect the probability of other atopic diseases, type 1 diabetes, or obesity diagnoses. The results from our supplementary empirical strategy based on within sibling variation in birth mode support our main findings. Moreover, we provide several sensitivity checks that suggest that the effect on asthma is unlikely to be explained by selection alone. Overall, our results paint a more nuanced picture about the long-term consequences of cesarean deliveries than existing evidence based mostly on associations. Our results suggest that C-sections cause a much narrower spectrum of diseases than currently hypothesized.