Military Moms Matter Act of 2021 This bill addresses Department of Defense (DOD) policies regarding parental leave and postpartum care for service members. The bill authorizes primary caregivers to take 12 weeks of parental leave, and up to 6 weeks of medical convalescent leave (which may not be considered in calculating the 12 weeks of parental leave), in connection with the birth of a child. Additionally, primary caregivers are authorized to take up to 12 weeks of parental leave in connection with the adoption of a child. Under the bill, secondary caregivers are authorized to take up to 12 weeks of parental leave in connection with the birth or adoption of a child. The bill also removes the requirement that secondary caregivers must take such leave in one increment. Among other requirements, DOD must also provide at least four postpartum mental health assessments and other medical care in the year after a service member (or their dependent) gives birth, ensure that a service member (or their dependent) who gives birth at a military medical treatment facility has the option to schedule a postpartum follow-up appointment concurrent with the date of the follow-up appointment for postnatal care for the newborn infant, develop a standardized policy prohibiting each military branch from requiring a service member to take a physical fitness test until one year after giving birth, and issue guidance on the development and implementation of standard protocols for the treatment of obstetric hemorrhages.