Cross-Sectional Associations Between Exposure to Commercial Milk Formula Marketing, Beliefs About Its Use, and Socioeconomic Position Among Pregnant Women and Mothers in the UK.

International provisions are in place to restrict marketing practices that idealise the use of commercial milk formula (CMF) and discourage breastfeeding. In high-income countries, women of lower socioeconomic position (SEP) are less likely to breastfeed. This study aimed to characterise the nature of exposure to CMF marketing in the UK, the extent to which women hold positive beliefs about CMF and examine the relationship between exposure to CMF marketing, holding positive beliefs about CMF and SEP. Data on these topics were collected for 1052 pregnant women and mothers of children under 18 months of age between February 2020 and February 2021. Participants were assigned a 'CMF marketing score' according to the number of locations where they recalled seeing advertisements, engaging with companies or receiving promotional activity. The extent to which women held positive beliefs about CMF ('CMF positivity score') was determined by level of agreement with 17 statements. Principal component analysis, analyses of covariance and regression analyses were applied. Every woman reported exposure to CMF marketing from multiple channels. CMF marketing score did not vary across SEP groups (p = 0.342). Women of lower and middle SEP held stronger CMF positive beliefs than women of higher SEP, including 'Breastfeeding and formula feeding provide a baby with the same health benefits' (p < 0.005). CMF marketing score was not associated with CMF positivity score. Marketing suggesting CMF provides benefits similar to, or greater than, breastfeeding should be restricted to help mitigate current inequalities in infant feeding practices.