Black Maternal Health Momnibus Act of 2020 This bill directs the Department of Health and Human Services (HHS) and other agencies to address maternal health outcomes among minority populations. HHS must (1) establish task forces to address social determinants of health, maternal mental and behavioral health, and other topics; and (2) award grants for maternal mortality review committees, innovative maternity care models, and other purposes. The Centers for Medicare & Medicaid Services must establish a perinatal payment demonstration project. The Department of Housing and Urban Development and the Department of Transportation must report on the impact of housing and transportation during prenatal and postpartum periods, respectively. The Department of Veterans Affairs must submit a plan for maternity care coordination for women veterans, and the Bureau of Prisons must establish programs and award grants to certain prisons and jails to improve maternal health outcomes among incarcerated individuals. The Government Accountability Office must report on the perinatal health workforce, maternity care compliance offices, and maternal health outcomes among veterans and incarcerated individuals. The National Academies of Sciences, Engineering, and Medicine must report on specified topics, including training programs to reduce bias, racism, and discrimination. The Medicaid and CHIP Payment Access Commission must report on the impact of Medicaid ineligibility on pregnant and postpartum individuals who are incarcerated. The bill also (1) expands eligibility for certain nutrition programs by increasing the postpartum and breastfeeding periods, and (2) reduces certain funding to states without laws restricting the use of restraints on pregnant women who are incarcerated.