Background: Allostatic load, a multisystem composite measure of chronic stress reflecting the cumulative wear and tear on the body, has utility in explaining maternal and child health disparities and predicting future health when measured during the peripartum period. Research using cross-sectional data has demonstrated an inverse association between concurrent breastfeeding status and maternal postpartum allostatic load. However, the relationship between breastfeeding duration and postpartum allostatic load has not been determined. Objective: This study aimed to examine the association between breastfeeding duration and postpartum allostatic load using prospective data, and to compare the association by race/ethnicity to better understand etiologies of health inequities. Materials and Methods: A secondary analysis of a data sample of 1,791 postpartum women from the Community Child Health Research Network was conducted. Multiple linear regression tested the association between and breastfeeding duration and allostatic load (range 0-10, calculated from 10 biomarkers) at 6 and 12 months postpartum, adjusting for race/ethnicity, maternal age, education, poverty level, study center, smoking, marital status, and prepregnancy body mass index. Stratified analyses examined differences in associations by race/ethnicity. Results: Breastfeeding duration was inversely associated with maternal allostatic load. In adjusted models, mothers who breastfed ≥6 months had 0.41 points lower allostatic load at 6 months (95% CI: -0.71 to -0.11) and 0.36 points lower allostatic load at 12 months postpartum (95% CI: -0.69 to -0.036) compared with mothers who never breastfed. Effect sizes varied in strength and significance across race/ethnic groups. Conclusions: Study findings suggest that extended breastfeeding for at least 6 months is linked with reduced chronic stress load in mothers during the first year postpartum. The inconsistency of findings across race/ethnic groups signals the importance of adjusting for prepregnancy allostatic load in future studies.
Keywords: allostatic load; breastfeeding; chronic stress; lactation; postpartum.