Placental abruption

Definition

Placental abruption occurs when the placenta separates from the wall of the uterus prior to the birth of the baby. This can result in severe, uncontrollable bleeding (hemorrhage).

Description

The uterus is the muscular organ that contains the developing baby during pregnancy. The lowest segment of the uterus is a narrowed portion called the cervix. This cervix has an opening (the os) that leads into the vagina, or birth canal. The placenta is the organ that attaches to the wall of the uterus during pregnancy. The placenta allows nutrients and oxygen from the mother's blood circulation to pass into the developing baby (the fetus) via the umbilical cord.

During labor, the muscles of the uterus contract repeatedly. This allows the cervix to begin to grow thinner (called effacement) and more open (dilatation). Eventually, the cervix will become completely effaced and dilated, and the baby can leave the uterus and enter the birth canal. Under normal circumstances, the baby will go through the mother's vagina during birth.

During a normal labor and delivery, the baby is born first. Several minutes to 30 minutes later, the placenta separates from the wall of the uterus and is delivered. This sequence is necessary because the baby relies on the placenta to provide oxygen until he or she begins to breathe independently.

Placental abruption occurs when the placenta separates from the uterus before the birth of the baby. Placental abruption occurs in about 1 out of every 200 deliveries. Afro-American and Latin-American women have a greater risk of this complication than do Caucasian women. It was once believed that the risk of placental abruption increased in women who gave birth to many children, but this association is still being researched.

Causes & symptoms

The cause of placental abruption is unknown. However, a number of risk factors have been identified. These factors include:

• Older age of the mother
• History of placental abruption during a previous pregnancy
• High blood pressure
• Certain disease states (diabetes, collagen vascular diseases)
• The presence of a type of uterine tumor called a leiomyoma
• Twins, triplets, or other multiple pregnancies
• Cigarette smoking
• Heavy alcohol use
• Cocaine use
• Malformations of the uterus
• Malformations of the placenta
• Injury to the abdomen (as might occur in a car accident).

Symptoms of placental abruption include bleeding from the vagina, severe pain in the abdomen or back, and tenderness of the uterus. Depending on the severity of the bleeding, the mother may experience a drop in blood pressure, followed by symptoms of organ failure as her organs are deprived of oxygen. Sometimes, there is no visible vaginal bleeding. Instead, the bleeding is said to be "concealed." In this case, the bleeding is trapped behind the placenta, or there may be bleeding into the muscle of the uterus. Many patients will have abnormal contractions of the uterus, particularly extremely hard, prolonged contractions. Placental abruption can be total (in which case the fetus will almost always die in the uterus), or partial.

Placental abruption can also cause a very serious complication called consumptive coagulopathy. A series of reactions begin that involve the elements of the blood responsible for clotting. These clotting elements are bound together and used up by these reactions. This increases the risk of uncontrollable bleeding and may contribute to severe bleeding from the uterus, as well as causing bleeding from other locations (nose, urinary tract, etc.).

Placental abruption is risky for both the mother and the fetus. It is dangerous for the mother because of blood loss, loss of clotting ability, and oxygen deprivation to her organs (especially the kidneys and heart). This condition is dangerous for the fetus because of oxygen deprivation, too, since the mother's blood is the fetus' only source of oxygen. Because the abrupting placenta is attached to the umbilical cord, and the umbilical cord is an extension of the fetus' circulatory system, the fetus is also at risk of hemorrhaging. The fetus may die from these stresses, or may be born with damage due to oxygen deprivation. If the abruption occurs well before the baby was due to be delivered, early delivery may cause the baby to suffer complications of premature birth.

Diagnosis

Diagnosis of placental abruption relies heavily on the patient's report of her symptoms and a the physical examination performed by a healthcare provider. Ultrasound can sometimes be used to diagnose an abruption, but there is a high rate of missed or incorrect diagnoses associated with this tool when used for this purpose. Blood will be taken from the mother and tested to evaluate the possibility of life-threatening problems with the mother's clotting system.

Treatment

The first line of treatment for placental abruption involves replacing the mother's lost blood with blood transfusions and fluids given through a needle in a vein. Oxygen will be administered, usually by a mask or through tubes leading to the nose. When the placental separation is severe, treatment may require prompt delivery of the baby. However, delivery may be delayed when the placental separation is not as severe, and when the fetus is too immature to insure a healthy baby if delivered. The baby is delivered vaginally when possible. However, a cesarean section may be performed to deliver the baby more quickly if the abruption is quite severe or if the baby is in distress.

Prognosis

The prognosis for cases of placental abruption varies, depending on the severity of the abruption. The risk of death for the mother ranges up to 5%, usually due to severe blood loss, heart failure, and kidney failure. In cases of severe abruption, 50-80% of all fetuses die. Among those who survive, nearly half will have lifelong problems due to oxygen deprivation in the uterus and premature birth.

Prevention

Some of the causes of placental abruption are preventable. These include cigarette smoking, alcohol abuse, and cocaine use. Other causes of abruption may not be avoidable, like diabetes or high blood pressure. These diseases should be carefully treated. Patients with conditions known to increase the risk of placental abruption should be carefully monitored for signs and symptoms of this complication.

Key Terms

Cesarean section

Delivery of a baby through an incision in the mother's abdomen, instead of through the vagina.

Labor

The process during which the uterus contracts, and the cervix opens to allow the passage of a baby into the vagina.

Placenta

The organ that provides oxygen and nutrition from the mother to the baby during pregnancy. The placenta is attached to the wall of the uterus and leads to the baby via the umbilical cord.

Umbilical cord

The blood vessels that allow the developing baby to receive nutrition and oxygen from its mother; the blood vessels also eliminate the baby's waste products. One end of the umbilical cord is attached to the placenta and the other end is attached to the baby's belly button (umbilicus).

Uterus

The muscular organ that contains the developing baby during pregnancy.

Vagina

The birth canal; the passage from the cervix of the uterus to the opening leading outside of a woman's body.

Further Reading

For Your Information

Books

• Cunningham, F. Gary et al. "Obstetrical Hemorrhage." In Williams Obstetrics, 20th Edition. Stamford, CT:Appleton & Lange, 1997.
• Pernoll, Martin L. "Third-Trimester Hemorrhage." In Current Obstetric & Gynecologic Diagnosis & Treatment, edited by Alan H. DeCherney and Martin L. Pernoll. Norwalk, CT: Appleton & Lange, 1994.

  Periodicals

• Lowe, T. W. and F. G. Cunningham. "Placental Abruption." Clinical Obsetrics and Gynecology 33 (September 1990): 406+.
• Bougere, M. H. "Abruptio Placentae." Nursing 28 (February 1998): 47+.

  Organizations

• The American College of Obstetricians and Gynecologists. 409 12th St., SW, PO Box 96920, Washington, DC 20090-6920. http://222.acog.com.

Gale Encyclopedia of Medicine. Gale Research, 1999.