Childhood maltreatment is associated with disruptions in narrative coherence about close relationships. The current pilot study introduced a brief new measure of narrative coherence about romantic partners, and tested whether post-traumatic stress disorder (PTSD) symptoms mediated the link between childhood maltreatment and narrative coherence about romantic partners during pregnancy. Participants were 101 low-income, ethnically diverse pregnant women (62% living below the poverty line; 37% Latina, 22% Black, 20% White, 22% other), with high rates of childhood maltreatment. They completed the Five-Minute Speech Sample about their romantic partner (i.e., the baby’s father) during pregnancy, which independent pairs of raters coded for prenatal narrative coherence and prenatal expressed emotion (including negative and warm affect) about partners. Participants also completed standardized self-report instruments assessing childhood maltreatment, romantic partner support, and prenatal PTSD and depression symptoms. Narrative coherence about partners from the Five-Minute Speech Sample showed convergent validity with romantic partner support and expressed emotion about partners. PTSD symptoms (but not depression symptoms) mediated the link between childhood maltreatment and prenatal narrative coherence about partners. The Five-Minute Speech Sample offers a brief and valid strategy to assess NC about romantic partners. PTSD symptoms and narrative coherence about partners are both potential intervention targets to promote healthy psychological and relational functioning during pregnancy.