Approximately 15 percent to 20 percent of diagnosed pregnancies end in miscarriage, usually within the first 13 weeks. Miscarriages can be threatened, where bleeding occurs but miscarriage doesn't occur; incomplete, meaning not all of the tissue is passed; missed, in which no tissue is passed but the fetus has died; and complete, meaning all tissue is passed. If a miscarriage occurs at home and bleeding continues, medical determination of the cause is necessary, even if it seems that all tissue passed.
Bleeding heavier than a normal period for one to two days or that continues more than seven days after a miscarriage is considered abnormal and needs investigation, according to the North Carolina Women's Hospital. Most bleeding tapers off, becoming lighter and scantier, fairly quickly after miscarriage. Saturating a pad in less than two hours is abnormally heavy bleeding and should be investigated, Boston Obstetrics and Gynecology states.
If bleeding continues after a natural miscarriage, there might still be fetal or placental tissue in the uterus. The uterus can't heal if retained material remains, so bleeding continues. Infection in the uterus also can cause heavy bleeding after miscarriage, even if all tissue is passed. A rare cause of bleeding after miscarriage is choriocarcinoma, a cancer that arises from placental tissue or after a molar pregnancy, in which placental tissue grows into an abnormal mass.
Retained tissue causes continued bleeding and cramping after a natural miscarriage. Symptoms of infection include continued bleeding, foul-smelling discharge, fever, chills and abdominal pain. Symptoms of choriocarcinoma after miscarriage include bleeding and pain, and a high beta hCG (pregnancy) level that doesn't drop after miscarriage, according to Medline Plus.
Most abnormal bleeding after a natural miscarriage requires a dilatation and curettage, a surgical procedure that scrapes the uterus, removing any tissue. A D&C is done under anesthesia in the hospital, often as an outpatient procedure. An infection in the uterus requires antibiotics. Choriocarcinoma usually requires chemotherapy.
Bleeding that's severe can result in a low red blood count, called anemia, or a need for blood transfusions, but this is rare. Untreated infection in the uterus can cause scar tissue inside the uterus and fallopian tubes, which can interfere with future pregnancy. Untreated choriocarcinoma can be deadly; cancer can spread to the liver or brain, Medline Plus warns. Hysterectomy is required in rare cases of severe bleeding.