If you have a normal menstrual flow, you are definitely not pregnant. Menstrual flow is mainly due to a drop in hormone levels prior to menstruation and exfoliative bleeding of the endometrium due to loss of support from high hormone levels, so pregnancy is not possible. However, there is a special case, which is when a patient has vaginal bleeding that may be mistaken for menstruation, but is not really menstruation, but vaginal bleeding due to an abnormal pregnancy, such as a preterm miscarriage or ectopic pregnancy. This type of bleeding is usually low in volume and the patient may bleed for a long or short period of time, mostly accompanied by cramping discomfort in the abdomen or pain in one side of the abdomen. The patient will need to have the blood chorionic gonadotropin, blood progesterone or ultrasound to make a comprehensive diagnosis. If the pregnancy is intrauterine, the pregnancy will need to be preserved according to the situation. If the pregnancy is ectopic, it will need to be treated conservatively or surgically, depending on the situation.