In this prospective cohort study, the prevalence of screening positive for PTSD was 9.4%, with similar rates for military (7.0%) and civilian (10.3%, P=.101) participants, and was associated with increased risk of depression and at-risk alcohol use (identified with a positive T-ACE screen result at the initial obstetrician visit at or before 16 weeks of gestation) but was not associated with adverse outcomes. This evidence concerns the gene ACE and post-traumatic stress disorder.