Methodological Integrity of Randomized Controlled Trials in Major Gynaecological Conditions: A Systematic Review

Background Randomized controlled trials (RCTs) provide the evidentiary foundation for clinical decision-making in obstetrics and gynaecology. However, concerns remain regarding methodological rigor, reporting transparency, and structural biases within women’s health research. Despite the global burden of gynaecological conditions such as endometriosis, polycystic ovary syndrome (PCOS), gestational diabetes mellitus (GDM), and premenstrual dysphoric disorder (PMDD), the methodological integrity of trials evaluating these conditions has not been comprehensively assessed. Methods This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines (PRISMA) and prospectively registered in PROSPERO (CRD42025636543). Electronic searches were performed in PubMed, ScienceDirect, and Google Scholar to identify RCTs published between January 2005 and October 2025 evaluating interventions for endometriosis, PCOS, GDM, or PMDD. Eligible studies included randomized or cluster-randomized trials involving adult women. Risk of bias was assessed using the Cochrane Risk of Bias 2 (RoB 2) tool. Reporting completeness was evaluated using the Consolidated Standards of Reporting Trials (CONSORT) 2010 checklist. Associations between trial-level characteristics and methodological quality were examined using logistic and linear regression analyses. Results A total of 695 RCTs were included in the review. Overall methodological quality was limited, with only 49 trials (7.0%) judged to be at low risk of bias. The most frequent concerns were related to outcome measurement and selective reporting. Sample sizes varied widely across conditions, with smaller trials predominating in PMDD and endometriosis research, while GDM trials tended to be larger. Prospectively registered trials demonstrated significantly higher reporting completeness, with an average increase of 8.6 percentage points in CONSORT adherence (p < 0.001), and were more likely to be classified as low risk of bias (OR 4.08, 95% CI 1.59–10.47). Reporting quality improved modestly over time but remained uneven across conditions and country income levels. Conclusions Trials with methodological limitations and variable reporting quality dominate the clinical evidence base for major gynaecological conditions. Prospective trial registration and transparency mechanisms were strongly associated with improved methodological standards. Strengthening trial design, enforcing reporting guidelines, and improving global equity in research infrastructure are essential to ensure that evidence guiding women’s health care is robust, transparent, and reliable.