Effect of vitamin D supplementation on follicular fluid BMP-15 protein and pregnancy rate in normal responder women undergoing intracytoplasmic sperm injection: a prospective comparative clinical study

Abstract Background Vitamin D (VD) is recognized for its essential function in several physiological processes, including reproductive health. Bone morphogenetic protein 15 (BMP-15), a key oocyte-derived growth factor, plays a critical role in folliculogenesis, oocyte maturation, and embryo development. This study investigates the effect of VD supplementation on follicular fluid BMP-15 protein levels and pregnancy rates in normal responder women undergoing infertility treatment, where intracytoplasmic sperm injection (ICSI) was performed on retrieved oocytes as part of the IVF process. Objective The objective was to determine whether VD supplementation influences BMP-15 concentration in follicular fluid and affects pregnancy outcomes. Methods A prospective comparative clinical study was conducted 90 women undergoing IVF treatment in which ICSI was performed on their oocytes, divided equally into two groups: a VD-supplemented group ( n = 45) and a control group ( n = 45). Follicular fluid samples were collected during oocyte retrieval to assess BMP-15 protein levels using ELISA. Results Women receiving VD supplementation exhibited significantly higher serum VD levels (24.1 vs. 18.2 ng/mL, p = 0.003), follicular fluid VD levels (24.3 vs. 18.6 ng/mL, p = 0.005), and follicular fluid BMP-15 protein levels (307.3 vs. 236.3 pg/mL, p = 0.002) compared with the control group. The chemical pregnancy rate was significantly higher in the VD group (62%) compared to the control group (44%, p = 0.047). Positive correlations were observed between follicular fluid VD levels and both BMP-15 concentrations ( p = 0.017) and chemical pregnancy outcomes ( p = 0.014). Conclusion VD supplementation may enhance follicular BMP-15 protein levels and improve pregnancy outcomes in women undergoing IVF treatment in which ICSI was performed on their oocytes. These findings support the role of VD in optimizing the ovarian microenvironment and highlight BMP-15 as a potential biomarker for oocyte competence and reproductive success.