Vitamin D has clinically recognized benefits for bone health, and its role extends to reproduction.[1] Previous studies in PCOS women undergoing in vitro fertilization (IVF) show that higher vitamin D status was associated with improved spontaneous ovulation and increased live birth rates.[1] Meta-analyses of vitamin D supplementation in women with polycystic ovary syndrome reported significantly improved pregnancy rates in the group receiving vitamin D supplementation.[1] Studies have found that vitamin D supplementation reduces C-reactive protein (a biomarker of chronic inflammation) and improves insulin resistance as measured by the HOMA-IR index in PCOS patients.[1] Vitamin D also affects testosterone levels and menstrual cycle regulation in women with PCOS and oligomenorrhea (infrequent periods).[1]