The Impact of Formula Industry Marketing on Breastfeeding Rates in Native and Migrant Mothers.

Lifelong benefits of breastfeeding are far-reaching. However, optimal breastfeeding practices may be negatively affected by the marketing of different forms of breast milk substitutes. In addition, whether market factors have a different impact on migrants' breastfeeding practices when compared to natives has been poorly investigated. Our study's aims are (1) to assess the effect of market factors on breastfeeding discontinuation (any and exclusive), (2) comparing migrant and native women. A longitudinal study was conducted within baMBINO, a nationwide project on perinatal health among migrant women in Portugal. Our final sample included 1,251 migrants and 1,150 natives recruited between April 2017 and March 2019 in 32 public maternities. Cox regression analysis was performed, adjusting for important confounders, and interactions were tested. Market factors were associated with any and exclusive breastfeeding discontinuation. Participants receiving free formula samples from a health professional were more likely to stop exclusive breastfeeding (adjusted hazard ratios [a] = 1.37, 95% confidence intervals [95% CI] = 1.13-1.66,  = 0.002). Reporting exposure to formula discounts was associated with discontinuation of exclusive (a = 1.22, 95% CI = 1.09-1.38,  = 0.001) and any breastfeeding (a = 1.21, 95% CI = 1.00-1.46,  = 0.046). No interactions were found between being migrant and exposure to market factors. Market factors influence discontinuation of any and exclusive breastfeeding. The impact of marketing does not differ between native and migrant women.