Social Determinants for Moms Act of 2020 This bill provides for a task force, grant programs, studies, and other activities concerning social determinants of health (SDOH) and their impact on maternal health outcomes, with a particular focus on areas with high rates of maternal mortality and severe maternal morbidity and racial and ethnic disparities in maternal health outcomes. The Department of Health and Human Services (HHS) must convene a task force to develop strategies to coordinate federal efforts to address SDOH for women in prenatal and postpartum periods, as well as provide guidance related to the use of certain Medicaid payments to address SDOH for high-risk mothers. HHS must also award grants to (1) expand access to free child care during prenatal and postpartum medical appointments, and (2) help public health departments reduce or eliminate certain disparities and improve maternal health outcomes by addressing SDOH. The bill also extends the postpartum and breastfeeding periods for purposes of eligibility for the Special Supplemental Nutrition Program for Women, Infants, and Children and directs the Department of Agriculture to establish a grant program to deliver healthy food to pregnant or postpartum women who live in food deserts.