Contraceptive injections are effective for about 3 months (short-acting contraceptive injections) to 1 year (long-acting contraceptive injections). The principle of contraceptive injection is basically the same as that of oral contraceptive pills, that is, through intramuscular injection of contraceptive components to maintain the concentration of contraceptive components in the blood of an individual, which in turn inhibits ovulation, changes the environment of the uterine cavity or the cervical mucus, and reduces the effectiveness of fertilized egg implantation, thus realizing contraception. Contraceptive injection is also divided into long-acting and short-acting, short-acting can generally maintain the contraceptive effect of 2-3 months, the long-acting can maintain the contraceptive effect of 1 year. Contraceptive injection is mainly progestin, with appropriate estrogen, after injection into the body, the drug is stored in the local area, and then slowly released to achieve the purpose of contraception. The side effects of contraceptive injection are the same as those of oral contraceptive pills, such as prolonged or shortened menstrual cycle, irregular vaginal bleeding, etc., accompanied by other symptoms such as dizziness, fatigue, drowsiness, nausea and so on. The contraceptive effect of the contraceptive injection is more than 99% effective, the disadvantage is that after stopping the contraceptive injection, the normal physiological functions need to be restored after a period of time, if you want to get pregnant, you need to stop using the drug, and the preparatory period should be about 6-24 months.