To evaluate factors associated with uptake of a financial incentive for developmental screening at an enhanced 18-month well-child visit (EWCV) in Ontario, Canada.

Population-based cohort study using linked administrative data of children (17-24 months of age) eligible for EWCV between 2009 and 2017. Logistic regression modeled associations of EWCV receipt by provider and patient characteristics.

Of 910 976 eligible children, 54.2% received EWCV (annually, 39.2%-61.2%). The odds of assessment were lower for socially vulnerable children, namely, those from the lowest vs highest neighborhood income quintile (aOR, 0.84; 95% CI, 0.83-0.85), those born to refugee vs nonimmigrant mothers (aOR, 0.90; 95% CI, 0.88-0.93), and to teenaged mothers (aOR, 0.70; 95% CI, 0.69-0.71)). Children were more likely to have had developmental screening if cared for by a pediatrician vs family physician (aOR, 1.28; 95% CI, 1.13-1.44), recently trained physician (aOR, 1.38; 95% CI, 1.29-1.48 for ≤5 years in practice vs ≥21 years) and less likely if the physician was male (aOR, 0.64; 95% CI, 0.61-0.66). For physicians eligible for a pay-for-performance immunization bonus, there was a positive association with screening.

In the context of a universal healthcare system and a specific financial incentive, uptake of the developmental assessment increased over time but remains moderate. The implementation of similar interventions or incentives needs to account for physician factors and focus on socially vulnerable children to be effective.