Women’s menstrual cycle, follicle recruitment in the late corpus luteum, the first day of menstruation follicle is the smallest, at this time the use of compound short-acting oral contraceptives to inhibit follicle, the effect is the best. If you don’t take it on the first day, and then take it on the second or fifth day, the follicles will grow slowly, and then use the compound short-acting oral contraceptive pill to inhibit follicle development, the effect is not so good, and the follicle grows up and then start to contraception, which is likely to lead to contraceptive failure. The mechanism of inhibition of follicular development by high potency estrogen and progesterone is negative feedback, acting on the hypothalamic-pituitary-ovarian axis, which can inhibit follicular development, so it is recommended that the compound short-acting oral contraceptive pill must be taken orally on the first day of menstruation.