Each year approximately 700 people die in the United States from pregnancy-related complications. We describe the characteristics of pregnancy-related deaths due to mental health conditions, including substance use disorders, and identify opportunities for prevention based on recommendations from fourteen state Maternal Mortality Review Committees (MMRCs) from the period 2008-17. Among 421 pregnancy-related deaths with an MMRC-determined underlying cause of death, 11 percent were due to mental health conditions. Pregnancy-related mental health deaths were more likely than deaths from other causes to be determined by an MMRC to be preventable (100 percent versus 64 percent), to occur among non-Hispanic White people (86 percent versus 45 percent), and to occur 43-365 days postpartum (63 percent versus 18 percent). Sixty-three percent of pregnancy-related mental health deaths were by suicide. Nearly three-quarters of people with a pregnancy-related mental health cause of death had a history of depression, and more than two-thirds had past or current substance use. MMRC recommendations can be used to prioritize interventions and can inform strategies to enable screening, care coordination, and continuation of care throughout pregnancy and the year postpartum.