If brown blood appears at 6 weeks of pregnancy, consider preterm miscarriage or ectopic pregnancy. The gestational sac has just formed at 6 weeks of pregnancy and is still very unstable in the uterus, so it is very easy to have a preterm miscarriage. Brown blood in the vagina is considered to be the discharge of old blood from the uterus, and it is recommended to go to the hospital as soon as possible for an ultrasound and blood tests to see the values of progesterone and human chorionic gonadotropin in the body. Ultrasound examination can reveal a gestational sac in the uterus, the size of which corresponds to the gestational week. If no gestational sac is found in the uterus, we need to find the cause and treat the ectopic pregnancy under the guidance of the doctor.