Health Disparities
Intersectional Multilevel (MAIHDA) Analysis of Preterm Birth Disparities in the United States Meredith Cahill* Meredith Cahill Claire Margerison
Preterm birth (PTB) impacts about 10% of U.S. births and is associated with increased morbidity, mortality, and healthcare burdens. Disparities by maternal race/ethnicity, nativity, age, education, and parity suggest that intersectional structural inequities may shape risk. Grounded in an ecosocial framework, we used Intersectional Multilevel Analysis of Individual Heterogeneity and Discriminatory Accuracy to examine PTB disparities across axes of maternal social identity, focusing on group differences, discriminatory accuracy, and interaction effects to deepen understanding of PTB disparities and identify high-risk groups. Using 2018-2019 natality data (n=7,008,531; PTB prevalence=9.9%), we grouped observations into 264 strata defined by maternal race/ethnicity, nativity, age, education, and parity. We used generalized linear mixed-effects models with a binomial-logit link to assess variability in PTB among strata. Predicted probabilities of PTB ranged from 5.2% (95%CI:4.4-6.2) to 28.4% (95%CI:25.5-31.6) and were highest among non-Hispanic (NH) Black, U.S.-born women 35+ years of age with ≤high school education, and lowest among NH-White, foreign-born women <35 with a college degree. Stratum-level differences explained 3.8% of total variation in probability of PTB, with the greatest proportion attributable to education (33.1%), age (24.8%), and race/ethnicity (22.9%). Overall, main effects accounted for 90.7% of variation, with 9.3% attributable to interactions. Significant random effects occurred for 91 of the 264 strata (Figure 1). These findings suggest within-stratum differences drive variations in PTB, but structural factors like educational status and race/ethnicity also contribute to variation. The finding that some variation in PTB is attributable to interaction effects combined with significant random effects in many strata indicates that intersectional inequities in PTB also exist.
