Antenatal mental disorders compromise maternal and child health, and women who have experienced childhood trauma may be at increased risk for such disorders. One hypothesis is that early trauma leads to the development and use of maladaptive coping strategies as an adult, which in turn could predict mental health difficulties during stressful transitions such as pregnancy. To test this hypothesis, this study examined the relationship between childhood trauma and mental health (depression, PTSD) in a sample of 84 pregnant women seeking antenatal care in Cape Town, South Africa, and explored whether maladaptive coping mediated this relationship. The majority of women (62 %) met established criteria for antenatal depression and 30 % for antenatal PTSD; in addition, 40 % reported a history of childhood trauma. Childhood trauma, especially childhood sexual abuse and emotional abuse, was significantly associated with depression and PTSD. The relationships between childhood trauma and depression and PTSD were significantly mediated by maladaptive coping, even when adjusted for the woman's age, gestational age, and HIV status. Findings highlight the need for coping-based interventions to prevent and treat antenatal mental disorders among women with childhood trauma, particularly in high-trauma settings such as South Africa.