Association between trajectories of breastfeeding duration and infant health: Prospective cohort study

Background: Breastfeeding is a modifiable pathway contributing to infant health. Objectives: To estimate trajectories of breastfeeding and the association between trajectories of breastfeeding and infant health. Methods: We conducted a prospective longitudinal cohort study (2014-2020, Canada) with 3217 cohabitating English-literate mother-father-infant triads with internet or telephone access. Women with major psychiatric conditions or suicidality were excluded. Data were collected online at baseline (<3 weeks postpartum), 3, 6, 9, 12, 18, and 24 months. Breastfeeding was measured at 0-12 months. Baseline measures included attention-deficit disorder with/without hyperactivity (ADHD, Adult ADHD Self-Report Scale) and childhood adversity (Adverse Childhood Experiences International Questionnaire). We measured infant health at 12-24 months using the Brief Infant-Toddler Social and Emotional Assessment (challenging behaviors) and self-reported number of emergent visits (>90th percentile). We estimated trajectories of breastfeeding using latent class growth analysis. Associations were estimated using adjusted linear mixed models. Results: Most included mothers (n=2548) were of Canadian birth (2078/2548, 82%) and graduated from university (1920/2548, 75%); few reported unemployment (222/2548, 9%) or prenatal depression (240/2548, 9%). We identified two trajectories of breastfeeding: Constant Breastfeeding (1522/2548, 60%) and Decreasing Breastfeeding (1026/2548, 40%). No statistically significant differences were observed between classes for either the risk of challenging behaviors (RR -0.006 95% CI -0.028 to 0.016) or the risk of emergent visits (RR -0.015 95% CI -0.053 to 0.023). Conclusions: In this study, discontinued breastfeeding was not associated with infant health. Future studies should focus on 6-month exclusive breastfeeding, a modifiable therapeutic infant feeding target.