The aim of this study was to explore the associations of health, gender, and motherhood with the decisions about breastfeeding. The sample consisted of 265 pregnant women (mean age: 32.34, SD: 4.01 years) who were recruited in healthcare centers and hospitals in southeast Spain between 2010 and 2011. Mental health was measured by the 12-Item General Health Questionnaire and gender by the Conformity to Feminine Norms Inventory. Women in our sample showed a higher conformity to gender norms than women surveyed in the adaptation of the inventory to the Spanish population (t = 11.25, p < 0.001, effect estimate (Cohen's d) = 0.59). After adjustment for covariates, women who exclusively breastfed did not differ significantly in their conformity to gender norms from those who used partial breastfeeding or bottle feeding. Although good, our expectant mothers had worse mental health than the women aged 15-44 years in the Spanish National Health Survey (t = 2.96, p < 0.001, d = 0.26). Those who partially breastfed had significantly better mental health values. Gender norms were modulators in a model of factors related to initiation of breastfeeding. This study provides information about health and social construction of gender norms.