The Expanded Biopsychosocial Model Elucidates the Association Between Pre‐Pregnancy Overweight/Obesity and Delayed Lactogenesis II: A Prospective Cohort Study

Pre‐pregnancy overweight or obesity delays the onset of lactogenesis II, posing an early barrier to achieving optimal infant nutrition and long‐term health. However, the underlying pathophysiological mechanisms remain incompletely elucidated. This prospective cohort study conducted in China aimed to delineate the distinct pathways through which pre‐pregnancy overweight/obesity, compared to normal body mass index (BMI), leads to delayed lactogenesis II. Guided by an expanded biopsychosocial framework, we enrolled and stratified 296 primiparous women into pre‐pregnancy overweight/obese ( n  = 146) and normal BMI ( n  = 150) groups. Data on biological, psychological, social, and infant‐related factors were collected prospectively at prenatal, delivery, and one‐week postpartum stages. Structural equation modeling was used to identify and compare the mediating pathways between the two groups. Results demonstrated that the association between pre‐pregnancy overweight/obesity and delayed lactogenesis II was primarily mediated through four distinct pathways: biological (e.g., breastfeeding difficulties: β  = 0.203, 95% CI: 0.144−0.265, p  < 0.001), psychological (e.g., internalized weight stigma: β  = 0.095, 95% CI: 0.016−0.181, p  = 0.026), social (e.g., reduced pro‐breastfeeding practices: β  = 0.076, 95% CI: 0.017−0.144, p  = 0.019), and infant‐related (e.g., higher formula intake: β  = 0.114, 95% CI: 0.047−0.195, p  = 0.003). This study validates the expanded biopsychosocial model by elucidating the distinct pathways through which pre‐pregnancy overweight/obesity contributes to delayed lactogenesis II. These findings underscore the necessity for clinical practice to move beyond a purely biological focus and advocate for a paradigm shift in clinical support towards integrated, multi‐faceted interventions tailored to this vulnerable population.

Trial Registration

This study was registered at the Chinese Clinical Trial Registry (registry number: ChiCTR2200057038). The trial was registered on February 26, 2022.