Association of Ethnicity With Ovarian Reserve: A Systematic Review and Meta-Analysis.

BACKGROUND AND AIMS: Ovarian reserve markers are reported to differ across ethnic groups, though the sources of this variation are unclear. We aimed to document this variation and examine the environmental, nutritional, and sociocultural factors that may explain it. METHODS: Observational studies were included if they enrolled women aged 18-45 and reported ovarian reserve markers (AMH, AFC, or FSH) stratified by an explicitly defined ethnicity classification. Four databases were searched. Risk of bias was assessed with the Joanna Briggs Institute checklist. A random-effects meta-analysis estimated standardized mean differences (SMD) with 95% confidence intervals (CI) and prediction intervals; heterogeneity was assessed with τ2 and I2. The two-study FSH comparison was treated as exploratory. RESULTS: Ten studies (10,349 women, nine countries) were included in the narrative synthesis; six contributed to the AMH meta-analysis and two to the exploratory FSH analysis. Most studies (7/10) had a low risk of bias. Individually, most studies reported higher ovarian reserve markers in White European women than in women of Middle Eastern, South Asian, or some Latin American or African descent. The pooled estimates for Asian versus European women were not statistically significant and were accompanied by extreme heterogeneity: AMH (6 studies: SMD -0.68, 95% CI -1.84 to 0.48; p = 0.19; I2 = 99.1%) and FSH (2 studies: SMD -1.36, 95% CI -15.25 to 12.54; p = 0.43; I2 = 89.8%). The wide FSH interval reflects the fragility of pooling only two studies. CONCLUSION: The consistent, clinically relevant finding here is qualitative: individual studies repeatedly report lower ovarian reserve markers outside White European populations, most plausibly reflecting environmental, nutritional, and socioeconomic exposures rather than fixed biology. The pooled estimates are exploratory given the small number of studies and near-total heterogeneity, and should not be over-interpreted. Population-specific AMH reference ranges, informed by studies that rigorously adjust for these confounders, are needed for equitable clinical decision-making. TRIAL REGISTRATION: PROSPERO Registration: CRD420251026342.