It is impossible to have menstruation after pregnancy, pregnancy does not have menstruation, it is possible that abnormal vaginal bleeding as menstrual blood, need to exclude miscarriage, ectopic pregnancy, cervical polyps and other pregnancy complications. 1. Miscarriage: before 28 weeks of pregnancy, pregnant women first appear vaginal bleeding, followed by paroxysmal lower abdominal pain, some patients may be accompanied by dilatation of the uterine orifice, the discharge of pregnancy, some pregnant women may be abnormal vaginal bleeding at this time as menstruation, this will delay the condition, endangering the life of the mother and fetus, the need for timely fertility preservation treatment or timely removal of the uterus. 2. Ectopic pregnancy: If the fertilized egg is deposited outside the uterine cavity, it will lead to ectopic pregnancy. If the gestational sac ruptures, sudden lower abdominal pain on one side of the body can occur around 8 weeks of pregnancy, accompanied by a small amount of vaginal bleeding, and those with heavy bleeding will have symptoms of shock. There will be non-clotting blood after puncture of the posterior vaginal fornix. It needs to be treated by laparoscopic surgery in time. 3. Cervical polyps: If the cervical polyps of pregnant women are too large or multiple, then irregular vaginal bleeding may occur during pregnancy, you can choose polypectomy, but pay attention to inhibit contractions and other fertility preservation treatment. It is recommended that those who have irregular bleeding during pregnancy consult a medical professional for treatment in order to avoid delays.