Physician networks and the rise of elective obstetric interventions

Cesarean sections and inductions in low-risk pregnancies have risen dramatically in recent decades, yet the drivers of these trends remain debated. This study examines peer influence within physician networks as a contributing factor. Using 170,151 New Jersey low-risk births from 1997 to 2014, linked to hospital discharge and physician office location data, we examine whether physicians' practices are associated with their peers' recent behaviors. We define peer groups by geographic proximity, shared hospital affiliation, and co-attendance frequency, and estimate multilevel logistic and Poisson regression models. A physician's likelihood of performing an intervention increases as the number of interventions performed among their peers increases, especially when the expected probability of peer-physician interaction increases. After 2007, peer influence on C-section use declined, aligning with new professional guidelines and policy efforts intended to discourage elective C-sections, while peer effects for inductions persisted. We argue this pattern may suggest that peer influence is stronger under conditions of high clinical discretion and tends to weaken as professional standards become more clearly defined and actively enforced. Findings suggest that social influence within physician networks is a subtle yet significant driver of practice change, shaped by tie strength and institutional context. This study provides new evidence contributing to our understanding of the rise in elective obstetric interventions and the conditions of diffusion.