Different types of birth control pills have different effects on menstruation, which should be analyzed on a case-by-case basis and should not be generalized. Oral emergency contraceptives mainly block the ovulation process of the ovaries, so it may lead to endocrine disorders, early or delayed menstrual cycle and changes in menstrual volume in women. Among them, regular use of long-acting or short-acting contraceptive pills has little effect on menstruation. Emergency contraceptive pills may change the menstrual cycle, but it will gradually return to normal for 1-2 months more. In addition, if the emergency contraceptive pill is used in the second half of the menstrual cycle, the duration of the effect may be extended accordingly, so it is recommended that the number of emergency contraceptive pills taken should not be more than 3 times a year. In contrast, regular use of long-acting or short-acting contraceptives can play a role in regulating menstruation to a certain extent, and a small number of them may have a reduced menstrual flow, but generally do not affect the menstrual cycle. Therefore, it is usually recommended to take safer forms of contraception, such as taking long-acting or short-acting pills, birth control rings, and condoms to reduce the harm to the body.