Bleeding in the first month of pregnancy can be caused by bleeding from fertilized egg implantation, pre-eclampsia, ectopic pregnancy, pregnancy combined with cervical lesions and external stimulation. 1.Bed-breeding bleeding of fertilized egg: After the fertilized egg is formed in the fallopian tube, it needs to move to the uterus and then choose a suitable location in the uterine cavity for further development, which is called bed-breeding. During the process of fertilization, the endometrium of the uterus will be destroyed and some pregnant women may experience a small amount of vaginal bleeding or brown discharge, which is a normal phenomenon. 2. Pre-eclampsia abortion: If the patient has been diagnosed with intrauterine pregnancy in the past and has irregular small amount of vaginal bleeding in the early stage of pregnancy, except for bleeding caused by vaginal and cervical lesions and obvious external factors (external impact on the abdomen, intercourse, etc.), pre-eclampsia abortion should be considered and prompt medical consultation is needed. The cause of miscarriage may be insufficient hormone level (HCG or progesterone) or spontaneous miscarriage caused by congenital abnormal development of the embryo (chromosomal abnormalities of both parents), mostly due to the superiority and inferiority of the embryo. 3.If the pregnant woman has not clearly intrauterine early pregnancy in the past: positive urine test paper at home only, bleeding in one month of pregnancy does not exclude the possibility of ectopic pregnancy, which can be accompanied by abdominal pain, abdominal mass, and even syncope and shock. The bleeding that occurs in ectopic pregnancy mostly stays in the abdominal cavity and the vaginal bleeding is not much, but with the gradual increase of abdominal bleeding, the condition progresses rapidly and hemorrhagic shock, DIC or even life-threatening may occur, so the pregnant woman must seek medical attention in time for a clear diagnosis.