Response to Verd et al. re: “Measures of Maternal Metabolic Health as Predictors of Severely Low Milk Production”

Dear Editor,

We appreciate the letter by Dr. Verd et al ¹ describing their observation a decade ago that an unfavorable lipid profile may be associated with early breastfeeding cessation. ² The persistent association between increasing maternal body mass index (BMI) and/or obesity presence and shortened breastfeeding duration across several large perinatal cohort studies suggests that women with obesity are at increased risk for lactation difficulties.^3–5 Given the known association of increasing BMI with insulin resistance and dyslipidemia, the role of metabolic health in milk production deserves further attention across the full translational research spectrum.

While existing perinatal cohort databases are one source of potential insights into the relation between measures of metabolic health and breastfeeding duration, it is important to recognize the limitations of these secondary analyses, which rely on breastfeeding duration as a proxy for the most salient outcomes, such as maternal milk production capacity and confirmation of primary milk production insufficiency. We need epidemiological research that enrolls cohorts during pregnancy to assess breastfeeding intentions, metabolic health indicators, and mammary development indicators, with continued close follow-up in the early postpartum period to differentiate primary lactation insufficiency from secondary causes of low milk supply such as infrequent breast emptying.

From our randomized trial of metformin to augment low milk supply ⁶ we learned that effective treatments for primary lactation insufficiency are likely to have more impact if initiated in pregnancy (or earlier) among those at high risk, rather than after low milk supply is identified. Development of such treatments is only possible with substantial investment in research aimed at early identification of those at risk for primary low milk supply and determination of mechanistic pathways. In other words, there is tremendous need for research to effectively address primary low milk supply identification, causes, prevention, treatment, and management.

In the meantime, these findings reinforce the importance of individualized breastfeeding management for the dyad with persistent low milk supply. Many of the women in our study shared how upsetting it was to be told they just needed to breastfeed more, or simply try harder. For medical providers, our findings underscore the importance of holistically evaluating patients with low milk supply and validating parents' genuine efforts at breastfeeding. For research scientists, our findings illuminate a path forward in this neglected area of endocrine research.