Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objective A pill containing ulipristal acetate (UPA) is used for emergency contraception (EC). Considering that, following its intake, spermatozoa may be exposed to UPA in the female genital tract we intended to evaluate sperm functions after incubation with this compound. Methods Motile spermatozoa were selected by swim-up and were incubated under capacitating conditions with UPA (at concentrations of 1, 10, 100, 1,000, and 10,000 ng/ml) or control medium. The main outcome measures were sperm vitality, sperm protein tyrosine phosphorylation (TyrP), spontaneous acrosomal reaction (AR), and human follicular fluid (hFF)-induced AR. Results Sperm vitality and TyrP pattern were similar between spermatozoa exposed to UPA or control. In addition, spontaneous AR ranged from 14.0. +/- 1.5% to 18.0. +/- 1.9% after exposure to UPA or control medium without significant differences, and UPA did not prevent hFF-induced AR. Conclusions Incubation of sperm with UPA at concentrations around the expected plasma levels after ingestion of this EC pill (similar to 100-200 ng/ml) did not modify the signal transduction of TyrP involved in sperm capacitation. Moreover, UPA showed no agonist effect on progesterone receptors because it did not induce AR. Considering that progesterone in hFF is essential for AR induction, and UPA did not prevent the hFF-induced AR, an antagonist action of UPA on the AR is unlikely.176428437Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)