The principle of contraceptives is mainly through the action of estrogen and progesterone, inhibit ovulation, affect the changes of the endometrium, affect the peristalsis of the fallopian tube, cervical mucus thickening, etc., to achieve the purpose of contraception. 1. Inhibit ovulation: Estrogen and progesterone increase in blood concentration after oral absorption, which affects the secretion of ovarian hormones through the feedback regulation of the gonadal axis, thus affecting ovulation. 2. affect the changes in the endometrium: if you take a short-acting contraceptive pill, it will cause the endometrium to shrink, and if it is an oral emergency contraceptive pill, it will lead to changes in the endometrium, which will have the effect of contraception. 3. Influence the peristalsis of the fallopian tubes: affecting the peristalsis of the fallopian tubes will affect the movement of the fertilized egg to the uterine cavity, thus affecting the implantation of the fertilized egg. 4. Cervical mucus thickening: cervical mucus will be thickened after oral contraceptive pills, which is not conducive to sperm penetration and affects pregnancy. Contraceptive pills are not suitable for all women and are recommended to be used under medical supervision.