Side effects of birth control pills, mainly gastrointestinal symptoms, vaginal bleeding and thromboembolism. In addition to its contraceptive role, the pill can also regulate menstruation. Contraceptive pills in the use of the process may appear a variety of side effects, common nausea, headache, irregular vaginal bleeding, breast pain, etc., rare thromboembolism, serious can lead to heart disease, stroke (cerebrovascular accidents), etc., may also appear liver function abnormalities, hypersensitivity reactions, and so on. There are many contraindications to the use of contraceptives, which need to be excluded before use. For example, it should not be used by women during pregnancy, and it should not be used by people who are allergic to the components of the drug. It should not be used by patients suffering from migraine, thromboembolic diseases, cardiovascular and cerebrovascular diseases, severe hypertriglyceridemia, abnormalities of liver and kidney function, malignant tumors of the reproductive organs or mammary glands, vaginal bleeding of unknown origin. Contraceptive pills, if used as treatment, should be used under medical supervision.