Purpose We sought to evaluate the extent to which childhood physical and/or sexual abuse history is associated with post-traumatic stress disorder (PTSD) during early pregnancy; and to explore the extent to which the childhood abuse-PTSD association is mediated through, or modified by, adult experiences of intimate partner violence (IPV). Methods In-person interviews collected information regarding history of childhood abuse and IPV from 2,928 women age 18–49 years old prior to 16 weeks of gestation. PTSD was assessed using the PTSD Checklist-Civilian Version (PCL-C). Multivariate logistic regressions were used to estimate odds ratios (OR) and 95% confidence intervals (CI). Results Compared to women with no childhood abuse, the odds of PTSD were increased 4.31-fold for those who reported physical abuse only (95%CI: 2.18–8.49), 5.33-fold for sexual abuse only (95%CI 2.38–11.98) and 8.03-fold for those who reported physical and sexual abuse (95%CI 4.10–15.74). Mediation analysis showed 13% of the childhood abuse-PTSD association was mediated by IPV. Further, high odds of PTSD were noted among women with histories of childhood abuse and IPV compared with women who were not exposed to either (aOR=20.20; 95%CI 8.18–49.85). Conclusions Childhood abuse is associated with increased odds of PTSD during early pregnancy. The odds of PTSD were particularly elevated among women with a history of childhood abuse and IPV. Efforts should be made to prevent childhood abuse and mitigate its effects on women’s mental health.