Divalent cation levels in serum and preovulatory follicular fluid of women undergoing in vitro fertilization embryo transfer.

In this controlled clinical study, we determined the serum and follicular fluid concentrations of the biologically active fractions of magnesium (Mg) and calcium (Ca) in 39 women undergoing controlled ovarian stimulation (COH) for in vitro fertilization (IVF) embryo transfer (ET). Serum levels of ionized Ca (Ca2+) and ionized Mg (Mg2+) were measured during day 3 of the IVF cycle, on the day of ovum pickup and 12 days following ET. Follicular fluid levels were measured on the day of ovum pickup. Serum levels of Mg2+ decreased and Ca2+ levels increased during the IVF cycle. Mg levels were significantly higher in follicular fluid than in serum. Ca2+ and Mg2+ may play a role in the preovulatory follicle, a possibility that warrants further study.