Diminished Ovarian Reserve with Markedly Elevated BPA Exposure in One of Two Monozygotic Twin Sisters Married to Monozygotic Twin Brothers

Abstract Background: Diminished ovarian reserve (DOR) in young women is commonly attributed to genetic factors; however, environmental endocrine-disrupting chemicals, particularly bisphenol A (BPA), have been increasingly implicated in ovarian dysfunction (1, 2, 4). Case: We report a unique case involving identical twin sisters married to identical twin brothers, minimising genetic, intrauterine, and partner-related confounding. One sister presented with infertility and DOR, while her genetically identical twin had preserved fertility. Environmental toxin analysis revealed a markedly elevated preconceptional urinary BPA level in the infertile woman, exceeding laboratory reference limits. In contrast, BPA concentrations in the other family members were within normal ranges.