Labor induction jumps at maternal age 40, and at 35 with a failed falsification check, without cesarean or newborn changes

Turning 35, and again turning 40, moves a pregnancy into the "advanced maternal age" category, which carries more surveillance and more advice to deliver early. Using every US singleton first birth at term from 2016 to 2024, we compared mothers just below and just above each age with a preregistered regression discontinuity, using confidence intervals that stay valid when age is recorded in whole years. Labor induction jumps by 1.19 percentage points at 35 (honest 95% CI 0.7 to 1.68). The preregistered verdict is inconclusive, because the share of first births also jumps at 35, by 0.4 points. At 40, induction jumps by 2.86 points (2.05 to 3.67), and that secondary test meets its confirm rule. Delivery at 39 weeks rises at both ages. Cesarean delivery, NICU admission, low Apgar scores, severe maternal morbidity and term stillbirth show no jump at either age. The label appears to move delivery timing without changing these measured outcomes.