Hormonal and Macronutrient Profiles in Human Milk Among Women with Low Milk Production

Adequate milk production is key for optimal infant growth, yet women often wean due to perceived low milk production (LMP). Maternal adiposity and gestational diabetes mellitus (GDM) are known potential risk factors for LMP and may alter both hormonal and macronutrient composition of human milk. This study aims to investigate the hormonal and macronutrient composition of human milk in relation to LMP, particularly in the context of maternal adiposity and GDM. Human milk samples were collected from 68 women with LMP and 160 women with normal milk production during 1–6 months postpartum. Of the 228 participants with the mean pre-pregnancy BMI of 26.3 ± 6.0 kg/m2, 80 (35.1%) had GDM. Concentrations of hormones (estrone, estradiol, progesterone, insulin, leptin, adiponectin) and macronutrients (fat, protein, lactose, glucose) were measured and compared between the two groups. Univariable and multivariable logistic regression analyses were conducted, adjusting for potential confounders such as maternal body mass index (BMI) and GDM, to assess the relationships between hormone and macronutrient concentrations, and milk production. Preliminary analyses indicated that higher concentrations of estrone (p < 0.001), leptin (p = 0.009), insulin (p = 0.002), protein (p = 0.012), and lactose (p = 0.004) were associated with LMP. After adjusting for maternal BMI and GDM in the univariable models, all of these associations remained, and progesterone (p = 0.045) also emerged as positively associated with LMP. In multivariable regression, followed by stepwise model selection, estrone (p < 0.001), protein (p < 0.001) and lactose (p = 0.015) demonstrated the strongest associations with LMP, with maternal BMI also contributing significantly (p = 0.010). The findings suggest that hormone and macronutrient concentrations in human milk may reflect LMP status and provide insights into the underlying biological mechanisms associated with LMP.