Women who experience withdrawal bleeding are considered to be using progesterone or taking the emergency contraceptive pill. Occasionally, the use of once in a while, the use of the uterus appear retreat bleeding, bleeding volume is small or normal menstrual volume is about the same, is normal, will not have too much impact on the body and harm. Progesterone and emergency contraceptive pills are hormonal drugs, after the use of retreat bleeding is also a side effect, occasionally use once is not too big, after a period of their own conditioning, will basically return to normal, if often use is easy to cause endocrine disorders, resulting in endocrine disorders, menstrual disorders, amenorrhea, is not recommended to often take emergency contraceptive pills contraception. Emergency contraceptive pills can only be taken once in six months to avoid adverse effects on the body.