The invention relates to the use of CD98 as endometrial receptivity marker permitting the development of methods to determine the optimum moment for blastocyst implantation based on the determination of the levels of expression of CD98 in the endometrial tissue during the cycle. The invention relates moreover to methods for increasing the receptivity of the endometrium based on the increase in levels of CD98 and, furthermore, to contraceptive compositions based on the use of CD98 inhibitors.