The common reasons why menstruation is basically over on the third day are as follows: 1. Generally, the number of days of menstruation for women is 4-6 days. If the previous period is more regular and the menstrual volume is more, and this time the menstrual volume is less and the menstrual volume is abnormal, you should first check whether you are pregnant; 2. Factors such as stressful life can cause a slight disruption of endocrine secretion, which can cause a decrease in menstrual volume; 3. If the symptom exists for a long time, you should consider whether there is a case of uterine cavity adhesion. Because the occurrence of uterine adhesions can lead to a thin endometrium, menstrual flow will be reduced, so be sure to go to the hospital for a specific examination. Especially for patients with a history of previous miscarriage, because miscarriage can cause damage to the endometrium, which can lead to cavity adhesions. Therefore, if you feel that your menstrual flow is low or suddenly decreases, especially after a miscarriage, you should go to the hospital for a relevant examination in time. If the menstrual flow is slightly reduced once in a while, there is no need to be nervous, as it may be an accidental situation, and you can observe it slowly in the future. These effects of birth control pills are actually immediate and basically have no effect on the body after stopping the pill, but any drug has side effects. If a woman is planning to get pregnant, she should choose condoms for contraception and try to avoid taking the pill for contraception. Clinically, some women with endocrine disorders need the pill to regulate their endocrine secretion. Such patients can apply it normally and do not need to be nervous or have concerns, taking the pill will not cause infertility.