Objective: Primary health service use (P-HSU) may be influenced by contextual characteristics and is equitable when driven by need. Contextual effects and inequity of maternal P-HSU were determined.

Methods: Participant data from a London-Middlesex, Ontario, prenatal cohort were linked by residential address to contextual characteristics. Multilevel logistic regression estimated contextual effects and tested for effect measure modification of need factors.

Results: Maternal P-HSU varied between neighbourhoods. The effect of obesity was different for rural mothers living in low- (OR = 0.26) and middle-income households (OR = 0.15) and for urban mothers living in high-income households (OR = 2.82). The effect of having a health condition was greatest in mothers with three or more children (OR = 2.41).

Discussion: Differences in maternal P-HSU exist between neighbourhoods, and enabling factors modified need factors' effects, identifying subgroups of mothers with inequitable P-HSU. RESULTS have the potential to inform Canadian health policy with regard to contextual effects and inequity of P-HSU.