Re: “Measures of Maternal Metabolic Health as Predictors of Severely Low Milk Production” by Nommsen-Rivers et al: Progression of Research to the Central Hypothesis That Waning Insulin Secretion Is an Important Cause of Low Milk Supply

Dear Editor,

Nommsen-Rivers et al ¹ have found that the lipid profile and most markers of the metabolic syndrome are substantially worse among women with severely low milk production than among their counterparts with moderate/normal milk output. However, the authors call for caution when it comes to confirming a consistent association between lipid metabolism dysregulation and impaired milk production, since their results were derived from a case–control study of only 42 participants. To the best of their own knowledge, theirs is the first trial to analyze the role of metabolic health parameters in persistent breastfeeding insufficiency. Hence, they conclude that it will be necessary to enroll a large longitudinal cohort starting in pregnancy to identify the maternal metabolic health indicators that are associated with insufficient milk production.

We think, on our part, that a prospective study that examined the relationship between maternal metabolic markers during pregnancy and breastfeeding success was undertaken a decade ago, ² but did not receive that attention it should. ³ From January 2003 to March 2004, all pregnant women living in Amsterdam were invited at their first prenatal visit to enroll in a longitudinal study ² ; women who used lipid-altering medication, who gave birth to twins, delivered preterm, or with known diabetes were excluded. Maternal variables were collected from a questionnaire and infant variables, including duration of exclusive breastfeeding from the youth health care centers.

A mother's blood sample for triglycerides and total cholesterol levels was taken after the first prenatal checkup. In the univariate analysis, 760 women who breastfed between 1 and 3 months had significantly higher total cholesterol levels than 986 women who breastfed beyond 3 months (5.00 ± 0.84 versus 4.91 ± 0.88 mmol/L; p = 0.029). Breastfeeding duration was not the first aim of this research, thus regression analysis was not used to estimate the effect of multiple variables on breastfeeding.

Most new mothers in western countries will start off breastfeeding. However, despite following best practices, some of them are not able to meet their breastfeeding goals. Dr. Nommsen-Rivers and coworkers timely remind us that the long-held belief that all mothers can successfully breastfeed their babies may not apply to women with metabolic syndrome. Since the current prevalence of metabolic syndrome among women at childbearing age in our culture ranges roughly from 13% ⁴ to 20%, ⁵ it is always worth the effort to reverse insulin resistance that has emerged as an important cause of low milk supply.