An extremely rare cause of vaginal bleeding during early pregnancy is a molar pregnancy. A molar pregnancy occurs when abnormal tissue grows rather than an embryo. This type of pregnancy is often referred to as gestational trophoblastic disease or GTD; it may also be called a "mole."
Vaginal bleeding during late pregnancy is often due to an inflamed cervix or cervical growths. Bleeding during late pregnancy may be a serious health risk to both the woman and the fetus, and may require hospitalization. Heavy vaginal bleeding during late pregnancy is, most often, an indicator of a problem with the placenta. The two most common problems that involve the placenta are placenta previa and placental abruption.
Placenta previa occurs in about one out of every two hundred pregnancies. If your placenta is laying low in the uterus it can cover all or part of the cervix. While many women experience placenta previa early in pregnancy, the placenta often moves before labor occurs. If a woman has placenta previa in the last weeks of pregnancy, a cesarean section will be scheduled. Placenta previa poses a serious risk to both the mother and the baby if it is not diagnosed and labor is allowed to occur; both the mother and baby are at risk of death in this situation. Vaginal bleeding during pregnancy is often the first sign of placenta previa.
Placental abruption occurs when the placenta detaches from the wall of the uterus either before or during labor; most often, placental abruption occurs during the last trimester of pregnancy. Vaginal bleeding may occur or not; most women will experience stomach pain even if they do not have any obvious bleeding. Fortunately, placental abruption occurs in only about one percent of pregnancies.
When labor arrives, many women will experience a "bloody show." This is when the plug that covers the opening of the cervix during pregnancy is passed shortly before birth occurs. This often contains a small amount of blood and mucous; it is quite common and not a health threat if it happens with a few weeks of your due date.
Remember anytime vaginal bleeding occurs during pregnancy, whether early pregnancy or late pregnancy, it should be reported to your health care provider.