July 18, 2021- A rigorous study showed that formula supplementation in the hospital decreased a mother’s likelihood of sustained exclusive breastfeeding. Hospital supplementation decreased her likelihood of initiating breastfeeding in a subsequent child by at least 66%, and reduced the duration of breastfeeding in any subsequent children by at least 6 weeks.

The study, by Mackenzie Whipps, PhD of New York University and colleagues, was published in Breastfeeding Medicine and used from data the national Infant Feeding Practices II survey. The authors used sophisticated techniques matching supplemented and non-supplemented infants in order to infer that these effects were caused by supplementation, and not merely markers of other issues.  

The authors postulate that the effect on breastfeeding subsequent children could come from a perception of insufficient milk supply, which could lead to negative feelings of breastfeeding in general.

The study has significant implications for formula marketing. The formula industry has long provided free samples of ready-to-use formula to hospitals, as well as in free discharge bags to new mothers. Because the samples are free, hospitals who contract with industry for free samples often do not lock up their formula supplies nor rigorously account for their use. Formula should be treated as a therapeutic intervention with specific medical indications in breastfed infants, and its use carefully documented. The authors of this study cite research estimating that one-quarter of US hospitals supplement at least 50% of healthy breastfed newborns with formula.

In this study, supplementation did not impact mothers’ intention to breastfeed subsequent children or to breastfeed as long as desired. This may be because intentions may change over time, perhaps to match a mother’s circumstances.