Gender Mix and Team Performance: Evidence from Obstetrics

We investigate how the gender mix of expert teams affects performance in a high-stakes setting: childbirth. Using data on 2.5 million births, we exploit the quasi-exogenous assignment of patients to two-member obstetrician teams (Lead–Assisting), and find that: (i) female-only teams achieve the best maternal outcomes, whereas male-only teams have the worst; and (ii) female-led mixed-gender teams perform worse than male-led ones. Specifically, severe maternal complications are 15.8% higher in male-only teams and 7.1-10.8% higher in mixed-gender teams compared to female-only teams. These patterns cannot be explained by patient risk, endogenous team formation, or physician preferences for discretionary practices like C-sections. Instead, gender mix directly affects team decisions and performance, likely through gender norms — a mechanism supported by two findings. First, gender mix affects how closely team decisions reflect member preferences, with female-only teams being especially skilled at this process, possibly due to more collaborative decision-making. Second, gender mix affects team resilience, with female-led mixed gender teams performing especially poorly under challenging conditions (e.g., limited team familiarity), possibly because female leaders invert traditional gender norms. We also document other notable patterns: female-only teams not only achieve the lowest complication rates for Black women, but are also the only team type to have no racial disparity in maternal outcomes. Overall, this study provides new insights into gender dynamics in expert teams, informing managerial efforts to support effective collaboration in increasingly diverse workplaces.