Brown blood in pregnancy may be due to miscarriage with precursor, ectopic pregnancy, cervical lesion, placenta praevia, preterm labor and so on. 1. Pre-eclampsia: In the early stage of pregnancy, due to certain reasons such as: environmental factors, maternal factors, etc., leading to pre-eclampsia, the symptoms of brown blood may occur. 2. Ectopic pregnancy: In the early stage of pregnancy, as the fertilized egg does not settle in the uterine cavity, but settles outside the uterine cavity, as the embryo continues to grow, it may rupture, causing the phenomenon of brown blood flow. 3. Cervical lesions: Some pregnant women who suffer from cervicitis or pre-cancerous lesions of the cervix may also have brown blood. 4. Placenta praevia: If the phenomenon of brown blood flow occurs in the late stage of pregnancy, it may be caused by placenta praevia, usually the bleeding is relatively small, and the pregnant woman does not have other uncomfortable symptoms. 5. Pre-eclampsia: If the phenomenon of bleeding brown blood occurs in the late stages of pregnancy, there is also the possibility of pre-eclampsia, and pregnant women may also be accompanied by lower abdominal pain, abdominal cramps, lumbago and other symptoms. If you have brown blood during pregnancy, it is recommended that you go to the hospital in time to determine the cause of the problem with the relevant tests and the specific week of pregnancy, and then treat the problem under the guidance of the doctor.