Impact of Periconceptional and Gestational Vitamin <scp>D3</scp> Restriction on Fetal Folliculogenesis and Anti‐Mullerian Hormone Secretion Using Sheep as a Model

Ovarian reserve is a reflection of the overall female reproductive potential. Vitamin D status has been suspected to influence fetal development and female fertility. As maternal diet during pregnancy can affect fetal development and future fertility, we hypothesised that periconceptional and gestational Vitamin D restriction could affect folliculogenesis and AMH secretion in the offspring. Nineteen sexually mature Welsh mountain ewes were randomly assigned to Vitamin D3 deficient (VDD, n = 10) and Vitamin D3 control (VDC, n = 9) diets from 17 days (d) before mating, up to 127-130 days of gestation, when fetal ovaries were collected (3 from VDC and 6 from VDD). Serum 25(OH)D3 concentrations were lower in VDD compared with VDC (p < 0.05). Relative to total follicle number, the percentage of primordial follicles was higher (p < 0.05), while the percentage of primary follicles was lower (p < 0.05) in VDD group compared with VDC group fetal ovaries. The integrated density value and percentage of affected area in TUNEL staining in VDD group did not vary from VDC group fetal ovaries (p > 0.05). Relative expression of AMH mRNA and AMH protein in VDD fetal ovaries were not statistically different compared with controls (p > 0.05). The relative expression of VDR mRNA were lower in VDD compared with VDC group fetal ovaries (p < 0.05). These data indicate that maternal Vitamin D dietary restriction is associated with ovarian tissue stemness and increased primordial follicle number but does not promote normal follicle recruitment or development in sheep fetal ovaries.