After you have taken the pill, it will affect your menstruation. Under normal circumstances, there are three kinds of birth control pills: 1. If you take the emergency contraceptive pill, there will be withdrawal bleeding of the drug in a week or so, and then the next menstruation will be based on withdrawal bleeding, and the cycle will be re-established, which may be early or wrong. After taking the pill, some people may not be able to get their periods. 2. Short-acting contraceptives can reduce the function of the ovaries, and the amount of menstruation may be high before, but after taking the pill, the amount of menstruation will become low. The effect of the cycle is not very big, short-acting contraceptive pill is counted from the first day of menstruation, eat 21 days in a row, and then the next menstruation to eat 21 days in a row. The short-acting contraceptive pill has little effect on menstruation, but it will affect the amount of menstruation, which will cause a significant reduction in the amount of menstruation than before, long-term eating, some people will also have endocrine disorders. 3, the long-acting contraceptive pill is a month to eat, if you want to stop the long-acting contraceptive pill after the child, you must stop the drug after six months before you can have children. This drug has a big impact on the human body and has a lot of side effects that can cause menstrual changes. All birth control pills have an effect on menstruation, the degree of impact on the human body varies, with the length of time to take the pill.