Objective
To examine the effects of a single-dose of 1.5 mg of levonorgestrel (commonly used as emergency contraceptive) on endometrial receptivity biomarkers through the oral or vaginal route. Design: Prospective randomized single-blinded trial. Setting: Affiliated Hospital and University Research Center. Patient(s): Fertile normal women previously sterilized by tubal ligation. Intervention(s): Levonorgestrel (1.5 mg) was administered on the day of LH surge either orally (n = 14) or vaginally (n = 13). Main outcome measure(s): Molecular assessment of endometrial progesterone receptors, L-selectin ligand, glicodelin-A and αvβ3 integrin by Immunohistochemistry and reverse transcriptase-polymerase chain reaction. Result(s): Plasma progesterone concentration and endometrial dating were not different. The pattern of progesterone receptors and glycodelin-A expression was not affected during the early and midsecretory phase. Some endometrial biopsies from the group in which levonorgetrel was orally administered showed areas of glandular atrophy and stromal decidualization. However, the expression of the progesterone receptor, L-selectin ligand, αvβ3 integrin, and glycodelin-A were not different between the groups.