Introduction: Polycystic ovary syndrome (PCOS) is the most prevalent endocrinopathy in reproductive aged women. The association of early-life factors such as fetal adipose tissue and birth weight with adulthood outcomes like obesity, body fat mass (BFM) and body lean mass (BLM) is not clearly understood. We aimed to compare the association between birth weight and body composition in women with PCOS and normal controls. Materials and Methods: For this study we enrolled a total of 70 reproductive aged women with PCOS diagnosis, referring to the Reproductive Endocrinology Research Center and the same number of healthy women without polycystic ovaries by ultrasonography or hirsutism and/or anyovulatory other dysfunction were enrolled. Their birth weights were documented and their body composition was assessed, using standard measuring devices. Results: Cases were younger than the controls (29.7±4.9 versus 30.8±5.9 years) and had the same BMI (24.6±2.4 versus 24.8±4.5 kg/m2). Our study demonstrated that BFM and BLM are increased in adult PCOS women born underweight, compared to their normal counterparts (16± 4.7 versus 12.2± 4.1, P= 0.06 and 46.4±5.8 versus 41.1±5.8, P=0.07). Conclusion: The impact of fetal adipose tissue and birth weight on the occurrence adulthood obesity, BFM and BLM vary between women with and without PCOS.