Parity Moderates the Socioeconomic Predictors of Birth Setting Choice.

Background: The increase in the number of people choosing community birth has raised interest in understanding the factors that influence birth setting choices. This study investigates how parity influences the association between maternal socioeconomic factors and choice of community versus hospital birth.

Methods: We used 2009-2021 US birth certificate data to identify community births (planned home or birth center births), parity, and maternal characteristics, including Women, Infants, and Children (WIC) program participation, race, ethnicity, educational attainment, marital status, body mass index (BMI), and age. Parity was interacted with each covariate in a multivariable logistic regression model of birth setting.

Results: Among 26,526,010 eligible births, 58% were to multiparous mothers, with 1.9% occurring in a birth center or at home. For most maternal characteristics, associations with community birth were stronger in the multiparous group compared to the nulliparous group. For example, being married was associated with greater odds of community birth in both groups, but the strength of this association was greater within the multiparous group (odds ratio 4.00 vs. 1.94, interaction p < 0.001). The same pattern (stronger association with community birth in the multiparous group than in the primiparous group) was observed for race/ethnicity, educational attainment, and WIC participation, all of which were associated with lower odds of community birth.

Conclusion: This study shows that parity significantly moderates associations between maternal socioeconomic characteristics and birth setting, implying studies of decision-making in this context should purposively stratify samples and analyses by parity.