Prenatal expectations describe various domains a woman envisions in preparation for her role as a new mother and influence how women transition into the maternal role. Although the maternal role is strongly influenced by the prevailing familial and sociocultural context, research characterizing prenatal expectations in ethnic minority and low-income women is lacking. As part of the largest growing minority group in the USA, Latina mothers represent an important group to study. Two hundred and ten low-income Mexican American women were administered the Prenatal Experiences Scale for Mexican Americans (PESMA) that was adapted to capture specific cultural aspects of prenatal expectations. Measures of current support, prenatal depressive symptoms, and other sociodemographic characteristics were also completed to assess validity. Exploratory factor analysis identified three underlying factors of prenatal expectations: paternal support, family support, and maternal role fulfillment. Associations among these subscales and demographic and cultural variables were conducted to characterize women who reported higher and lower levels of expectations. The PESMA demonstrated good concurrent validity when compared to measures of social support, prenatal depressive symptoms, and other sociodemographic constructs. A culturally sensitive measure of prenatal expectations is an important step towards a better understanding of how Mexican American women transition to the maternal role and identify culturally specific targets for interventions to promote maternal health.