Abstract Objectives This study aimed to investigate the characteristics of obstetrics and gynecology (OG) core outcome sets (COSs) and assess the report and design standards of OG COSs, and exploring how to improve baseline standards for obstetrics and gynecology COSs development. Study Design and Setting We conducted a comprehensive search of COMET database on December 20, 2019. Two reviewers independently evaluated whether the OG COS met the reporting requirement as stipulated in the Core Outcome Set-STAndards for Reporting (COS-STAR) statement checklist and the minimum design recommendations using the Core Outcome Set-STAndards for Development (COS-STAD) checklist. Results Forty-four OG COSs focused on 26 topics. None met all the 25 standards of COS-STAR statement representing 18 items considered essential for transparent and complete reporting in all COS studies (range: 6.0-24.0, median: 14.0 ). The compliance rates for the 16 standards of methods and result sections ranged from 27.3% - 68.2%. Total COS-STAR compliance items of OG COSs with the prior protocol was significantly higher than without prior protocol (MD= 3.846, 95% CI: 0.835 - 6.858, P= 0.012). None of the OG COSs met all the 12 criteria of COS-STAD minimum standards (range: 3.0-11.0, median: 5.0). The compliance rates for all three standards of stakeholders involved and all four standards of the consensus process were lower than 60%. Conclusion Methodological and reporting standards of OG COSs should be further improved.