OBJECTIVE: To evaluate the use of clinical trials registries in published obstetrics and gynecologic systematic reviews and meta-analyses. METHODS: We performed a metaepidemiologic study of systematic reviews between January 1, 2007, and December 31, 2015, from six obstetric and gynecologic journals (Obstetrics & Gynecology, Obstetrical & Gynecological Survey, Human Reproduction Update, Gynecologic Oncology, British Journal of Obstetrics and Gynaecology, and American Journal of Obstetrics & Gynecology). All systematic reviews included after exclusions were independently reviewed to determine whether clinical trials registries had been included as part of the search process. Studies that reported using a trials registry were further examined to determine whether trial data were included in the analysis of these systematic reviews. RESULTS: Our initial search resulted in 292 articles, which was narrowed to 256 after exclusions. Of the 256 systematic reviews meeting our selection criteria, 47 (18.4%) used a clinical trials registry. Eleven of the 47 (23.4%) systematic reviews found unpublished data and two included unpublished data in their results. CONCLUSION: A majority of systematic reviews in clinical obstetrics and gynecology journals do not conduct searches of clinical trials registries or do not make use of data obtained from these searches. Failure to make use of such data may lead to an inaccurate summary of available evidence and may contribute to an overrepresentation of published, statistically significant outcomes.