Pregnancy, Bleeding (cont.)
IN THIS ARTICLE
Late-Pregnancy Bleeding Causes
The most common cause of late-pregnancy bleeding is a problem with the placenta. Some bleeding can also be due to an abnormal cervix or vagina.
Placenta previa: The placenta, which is a structure that connects the baby to the wall of your womb, can partially or completely cover the cervical opening (the opening of the womb to the vagina). When you bleed because of this, it is called placenta previa. Late in pregnancy as the opening of your womb, called the cervix, thins and dilates (widens) in preparation for labor, some blood vessels of the placenta stretch and rupture. This causes about 20% of third-trimester bleeding and happens in about 1 in 200 pregnancies. Risk factors for placenta previa include these conditions:
Placental abruption: This condition occurs when a normal placenta separates from the wall of the womb (uterus) prematurely and blood collects between the placenta and the uterus. Such separation occurs in 1 in 200 of all pregnancies. The cause is unknown. Risk factors for placental abruption include these conditions:
Uterine rupture: This is an abnormal splitting open of the uterus, causing the baby to be partially or completely expelled into the abdomen. Uterine rupture is rare, but very dangerous for both mother and baby. About 40% of women who have uterine rupture had prior surgery on their uterus, including Cesarean delivery. The rupture may occur before or during labor or at the time of delivery. Other risk factors for uterine rupture are these conditions:
Fetal vessel rupture: This condition occurs in about 1 of every 1,000 pregnancies. The baby's blood vessels from the umbilical cord may attach to the membranes instead of the placenta. The baby's blood vessels pass over the entrance to the birth canal. This is called vasa previa and occurs in 1 in 5,000 pregnancies.
Less common causes of late-pregnancy bleeding include injuries or lesions of the cervix and vagina, including polyps, cancer, and varicose veins.
Pamela Dyne, MD