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High-Risk Pregnancy - Bleeding in Pregnancy / Placenta Previa / Placental Abruption

Bleeding may occur at various times in pregnancy. Although bleeding is alarming, it may or may not be a serious complication. The time of bleeding in the pregnancy, the amount, and whether or not there is pain may vary depending on the cause.

Bleeding in the first trimester of pregnancy is quite common and may be due to the following:

  • miscarriage (pregnancy loss)
  • ectopic pregnancy (pregnancy in the fallopian tube)
  • gestational trophoblastic disease (a rare condition that may be cancerous in which a grape-like mass of fetal and placental tissues develops)
  • implantation of the placenta in the uterus
  • infection

Bleeding in late pregnancy (after about 20 weeks) may be due to the following:

  • placenta previa (placenta is near or covers the cervical opening)
  • placental abruption (placenta detaches prematurely from the uterus)
  • unknown cause

What is placenta previa?

Placenta previa is a condition in which the placenta is attached close to or covering the cervix (opening of the uterus). Placenta previa occurs in about one in every 200 live births. There are three types of placenta previa:

  • total placenta previa - the placenta completely covers the cervix.
    Illustration demonstrating total placenta previa
    Click Image to Enlarge
  • partial placenta previa - the placenta is partially over the cervix.
    Illustration demonstrating partial placenta previa
    Click Image to Enlarge
  • marginal placenta previa - the placenta is near the edge of the cervix.
Illustration of marginal placenta previa
Click Image to Enlarge

What causes placenta previa?

The cause of placenta previa is unknown, but it is associated with certain conditions including the following:

  • women who have scarring of the uterine wall from previous pregnancies
  • women who have fibroids or other abnormalities of the uterus
  • women who have had previous uterine surgeries or cesarean deliveries
  • older mothers (over age 35)
  • African-American or other minority race mothers
  • cigarette smoking
  • placenta previa in a previous pregnancy

Why is placenta previa a concern?

The greatest risk of placenta previa is bleeding (or hemorrhage). Bleeding often occurs as the lower part of the uterus thins during the third trimester of pregnancy in preparation for labor. This causes the area of the placenta over the cervix to bleed. The more of the placenta that covers the cervical os (the opening of the cervix), the greater the risk for bleeding. Other risks include the following:

  • abnormal implantation of the placenta
  • slowed fetal growth
  • preterm birth
  • birth defects
  • infection after delivery

What are the symptoms of placenta previa?

The most common symptom of placenta previa is vaginal bleeding that is bright red and not associated with abdominal tenderness or pain, especially in the third trimester of pregnancy. However, each woman may exhibit different symptoms of the condition or symptoms may resemble other conditions or medical problems. Always consult your physician for a diagnosis.

How is placenta previa diagnosed?

In addition to a complete medical history and physical examination, an ultrasound (a test using sound waves to create a picture of internal structures) may be used to diagnose placenta previa. An ultrasound can show the location of the placenta and how much is covering the cervix. A vaginal ultrasound may be more accurate in diagnosis.

Although ultrasound may show a low-lying placenta in early pregnancy, only a few women will develop true placenta previa. It is common for the placenta to move upwards and away from the cervix as the uterus grows, called placental migration.

Treatment for placenta previa:

Specific treatment for placenta previa will be determined by your physician based on:

  • your pregnancy, overall health, and medical history
  • extent of the condition
  • your tolerance for specific medications, procedures, or therapies
  • expectations for the course of the condition
  • your opinion or preference

There is no treatment to change the position of the placenta. Once placenta previa is diagnosed, additional ultrasound examinations are often performed to track its location. It may be necessary to deliver the baby, depending on the amount of bleeding, the gestational age, and condition of the fetus. Cesarean delivery is necessary for most cases of placenta previa. Severe blood loss may require a blood transfusion.

What is placental abruption?

Placental abruption is the premature separation of a placenta from its implantation in the uterus. Within the placenta are many blood vessels that allow the transfer of nutrients to the fetus from the mother. If the placenta begins to detach during pregnancy, there is bleeding from these vessels. The larger the area that detaches, the greater the amount of bleeding. Placental abruption occurs about once in every 100 births. It is also called abruptio placenta.

What causes placental abruption?

Other than direct trauma to the uterus such as in a motor vehicle accident, the cause of placental abruption is unknown. It is, however, associated with certain conditions, including the following:

  • previous pregnancy with placental abruption
  • hypertension (high blood pressure)
  • cigarette smoking
  • multiple pregnancy
  • sickle cell anemia

Why is placental abruption a concern?

Placental abruption is dangerous because of the risk of uncontrolled bleeding (hemorrhage). Although severe placental abruption is rare, other complications may include the following:

  • hemorrhage and shock
  • disseminated vascular coagulation (DIC) - a serious blood clotting complication.
  • poor blood flow and damage to kidneys or brain
  • stillbirth
  • postpartum (after delivery) hemorrhage

What are the symptoms of placental abruption?

Illustration demonstrating concealed bleeding during pregnancy
Click Image to Enlarge

The most common symptom of placental abruption is dark red vaginal bleeding with pain during the third trimester of pregnancy. It also can occur during labor. However, each woman may experience symptoms differently. Symptoms may include:

  • vaginal bleeding
  • abdominal pain
  • uterine contractions that do not relax
  • blood in amniotic fluid
  • nausea
  • thirst
  • faint feeling
  • decreased fetal movements

The symptoms of placental abruption may resemble other medical conditions. Always consult your physician for a diagnosis.

How is placental abruption diagnosed?

Illustration demonstrating visible bleeding during pregnancy
Click Image to Enlarge

The diagnosis of placental abruption is usually made by the symptoms, and the amount of bleeding and pain. Ultrasound may also be used to show the location of the bleeding and to check the fetus. There are three grades of placental abruption, including the following:

  • Grade 1 - small amount of vaginal bleeding and some uterine contractions, no signs of fetal distress or low blood pressure in the mother.
  • Grade 2 - mild to moderate amount of bleeding, uterine contractions, the fetal heart rate may shows signs of distress.
  • Grade 3 - moderate to severe bleeding or concealed (hidden) bleeding, uterine contractions that do not relax (called tetany), abdominal pain, low blood pressure, fetal death.

Sometimes placental abruption is not diagnosed until after delivery, when an area of clotted blood is found behind the placenta.

Treatment for placental abruption:

Specific treatment for placental abruption will be determined by your physician based on:

  • your pregnancy, overall health, and medical history
  • extent of the disease
  • tolerance for specific medications, procedures, or therapies
  • expectations for the course of the disease
  • your opinion or preference

There is no treatment to stop placental abruption or reattach the placenta. Once placental abruption is diagnosed, a woman's care depends on the amount of bleeding, the gestational age, and condition of the fetus. Cesarean delivery is performed for most cases of placental abruption and emergency delivery may be needed if hemorrhage occurs. Severe blood loss may require a blood transfusion.

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