What happens when the findings of a prominent medical study are overturned? Using a medical trial on breech births, we estimate the effect of the reversal of such a medical study on physician choices and infant health outcomes. Using the United States Birth Certificate Records from 1995 to 2010, we employ a difference-in-differences estimator for C-sections, low Apgar, and low birth weight measures. We find that the reversal of a multi-site, high profile, randomized control trial on the appropriate delivery of term breech births, the Term Breech Trial, led to a 15%-23% decline in C-sections for such births at a time when the overall trend in C-sections was rising. We find our largest estimated effects amongst traditionally disadvantaged groups (i.e., non-white, and minimal education). However, we do not find that such a change in practice had significant impacts on infant health. Contrary to prior studies, we find that physicians updated their beliefs quickly, and do indeed adjust to new medical research, particularly young physicians, prior to mandatory policy or professional guidelines.

This paper examines the health effects of Caesarean section (CS) for children and their mothers. We use exogenous variation in the probability of CS in a fuzzy regression discontinuity design. Using administrative Danish data, we exploit an information shock for obstetricians that sharply altered CS rates for breech babies. We find that CS decreases the child\'s probability of having a low APGAR score and the number of family doctor visits in the first year of life. We find no significant effects for severe neonatal morbidity or hospitalizations. While mothers are hospitalized longer after birth, we find no effects of CS for maternal post-birth complications or infections. Although the change in mode of delivery for the marginal breech babies increases direct costs, the health benefits show that CS is the safest option for these children.