In hysteroscopic surgery, endometrial priming is key to the success of the intervention. Performing hysteroscopy in secretory phase of the menstrual cycle can significantly affect vision, making difficult the intervention and prolonging the operating time. Generally, we prefer to perform hysteroscopic interventions in early proliferative phase, during the first few days after menses. In cases in which is not possible, we inhibit endometrial growth with oral contraceptives.

However, in patients who require endometrial assessment for fertility treatments, it is better performed during the secretory phase, without endometrial preparation, since the administration of hormonal therapy may affect the normal endometrial development.

Endometrial quality assessment in regards to the timing of the menstrual cycle, determined by the presence of endometrial glandular grooves and openings reported by Sakumoto-Masamoto, classifies the endometrium as good or bad, for embryo implantation. The endometrium is classified as good for implantation if the endometrial glands presents openings ring type (ring-Type) with máximum glandular secretion, and classified as bad for implantation if it has punctate endometrial glands.