Sex- and gender-sensitive research can help to understand differences in prevalence, manifestation, and etiology of mental disorders. It is acknowledged that men and women are at different risks for traumatization as well as for the development of posttraumatic stress disorder (PTSD). In this systematic review and meta-analysis, we examine sex/gender differences in PTSD risk within five time-intervals ranging from 1 month to 5 years post-trauma, and analyze how sex and gender are considered in prospective studies on PTSD development (k=45). Women had higher PTSD burdens across timepoints but were underrepresented in research (68.5% male, 31.5% female participants). Only one study used sex as discovery variable. Sex and gender aspects in design, data, and discussion were considered by only one third of studies each. Trauma research falls short of its potential to adequately consider sex and gender. Sex- and gender-sensitive practices can advance rigor, innovation and fairness in clinical research.