There are more reasons for brown blood in 7 weeks of pregnancy, which may be caused by factors such as spontaneous abortion, ectopic pregnancy, cervical lesions, and hyperemesis gravidarum. 1. spontaneous abortion: chromosomal abnormality of embryo, illness of mother, chromosomal abnormality of sperm and other factors may cause spontaneous abortion, including preeclampsia and induced abortion, etc. The blood stays for a long time when it is in the vagina and the uterine cavity, and it may turn brown after oxidation. 2. Ectopic pregnancy: this disease mainly includes tubal pregnancy, ovarian pregnancy, abdominal pregnancy, etc. Patients may have vaginal bleeding, the bleeding is relatively small, and the blood stays in the uterine cavity for a long time, and after oxidation, it will turn brown. 3. Cervical lesions: when pregnant women suffer from cervicitis, cervical polyps and other cervical diseases, hormone level changes, inflammation stimulation and other factors, brown discharge may occur. 4. hyperemesis gravidarum: the disease is usually caused by abnormal proliferation of placental chorionic trophoblast cells, the patient may appear in the menopause 8 to 12 weeks of vaginal bleeding symptoms, the color may be dark brown, may also be bright red. There may also be other causes of brown blood in 7 weeks of pregnancy, and it is recommended that the patient consult a doctor in time to identify the cause of the disease and then carry out targeted treatment under the guidance of a professional doctor.