Taking birth control pills twice in half a month may affect your period and lead to menstrual disorders. Taking birth control pills twice in half a month that would have such a take is usually the emergency contraceptive pill. Emergency contraceptive pills are used when a woman is unprotected or when other methods of contraception fail, and are not recommended for frequent use, nor should they be used as a regular form of contraception. Emergency contraceptive pills may affect menstruation, causing early or delayed menstruation, and repeated use may cause menstrual disorders. After taking emergency contraceptive pills, women may also have mild nausea, vomiting, headache and other symptoms, usually do not need to be dealt with, can disappear after 24 hours. If irregular uterine bleeding occurs after taking the pill, you need to be alert to the presence of ectopic pregnancy. Contraindicated in pregnant women, patients with breast cancer, cardiovascular and cerebrovascular diseases, thrombosis disease, mental depression and women over 40 years old.