Is there an association between maternal weight and lactation?

A new study published online in the journal Advances in Nutrition analyzed associations between the mother's body size and lactation, including the time of onset, amount of milk produced, and infant consumption of the mother's own milk (MOM).

Breastfeeding is the ideal source of nutrition for almost all infants. However, only 44% of infants worldwide below six months of age are breastfed without supplementary feeds. One common reason is insufficient milk to satisfy the child's needs.While underweight mothers may not have adequate energy stores to form enough milk,obese mothers may be associated with hormonal and metabolic aberrations that suppress lactation.

In the study, researchers included 122 articles, with a total of over 42,500 mothers. The mean maternal age was between 20 years and 35 years. The mean body mass index (BMI) ranged from 16.7 to 31.3 kg/m2. The percentage fat mass ranged from 15.5 to 45.4.

The results showed that underweight or healthy-weight mothers were 35% less likely to experience delayed abundant breast milk production compared to obese or overweight mothers. Maternal BMI didn't affect onset time of copious milk. Infant milk consumption didn't correlate with maternal BMI or fat percentage, possibly due to limited energy intake variation or small sample size for obese women.

The findings suggested that obesity and overweight may delay abundant breast milk onset post-delivery compared to non-overweight mothers, but supporting data is limited due to mixed study results.

"Maternal obesity as a condition that impairs lactation.However, our results did not adequately capture mothers with preterm infants or those with a BMI >30kg/m2, who may be at greatest risk," said the study authors.

Reference: Montana, A. V., Mildon, A., Daniel, A. T., et al. Is maternal body weight or composition associated with onset of lactogenesis II, human milk production or infant consumption of mother's own milk? A systematic review and meta-analysis. Advances in Nutrition 2024. DOI: 10.1016/j.advnut.2024.100228, https://www.sciencedirect.com/science/article/pii/S2161831324000620