Brown blood at six weeks of IVF pregnancy can be caused by preeclampsia, cervical lesions and vaginitis. It can be treated by resting and using medication. 1. Pre-eclampsia: six weeks of pregnancy belongs to the early stages of pregnancy, when the gestational sac has just been formed, in the uterus is not very stable, it is easy to have pre-eclampsia, thus appearing in vitro six weeks of pregnancy with brown blood, often accompanied by abdominal pain. At this time, pregnant women should pay attention to bed rest, if the symptoms fail to improve, should follow the doctor’s instructions to take progesterone capsules and other drugs to protect the fetus treatment. 2. Cervical lesions: such as cervical polyps, stimulation of blood vessel rupture, may appear in vitro pregnancy six weeks with brown blood. At this time, the cause of the disease should be clarified, if the symptoms are mild, you can continue the pregnancy; if the bleeding occurs repeatedly, you can take surgical treatment. 3. Vaginitis: If a pregnant woman has vaginitis, once the local mucosa bleeds, there will be in vitro pregnancy six weeks with brown blood, mostly accompanied by vulvar itching and other symptoms. At this time, the pathogenic bacteria should be clarified, and medication should be used under the guidance of the doctor. If there is brown blood in six weeks of in vitro pregnancy, it is recommended to consult a doctor in time, under the guidance of the doctor, improve the relevant examination, to clarify the growth and development of the fetus.