Placental abruption

Definition

Placental abruption is a condition in pregnancy in which the placenta prematurely separates from the uterine wall while the fetus is still in utero. While it is seen most often during the third trimester of pregnancy, especially during the labor process, the term can be applied from 20 weeks gestation through term. Severe bleeding, even hemorrhage, can result, putting both the mother and fetus at significant risk. It is also known as placenta abruptio and abruptio placentae.

Description

In most cases placental abruption occurs in a normally implanted placenta, one that is located high on the uterine wall. However, it can occur in tandem with placenta previa. In a normal vaginal delivery, the delivery of the placenta follows that of the neonate within about 30 minutes. Because the neonate has been born and is now breathing on his or her own, the separation of the placenta from the uterine wall causes no distress. In placental abruption, however, the premature separation of the placenta deprives the fetus of the oxygen, nutrients, and gas exchange taking place at the site of the separation. The cost to the fetus depends on the degree and size of the separation. The risk to the mother depends on the amount of blood lost, the subsequent change in circulating blood volume, and its accompanying decrease in tissue perfusion.

Placental abruption occurs in about one in 120 deliveries. Severe abruption leading to fetal death occurs in about one in 420 deliveries. Cocaine use increases the risk of abruption by increasing vasoconstriction, and about 10% of mothers using cocaine in the third trimester succumb to placental abruption.

Causes and symptoms

The causes of abruption are not fully understood, but it appears that it may be the end result of a series of fetal-maternal vascular abnormalities. Impaired blood vessel integrity and suppressed immune function may lie at the core of the development of abruption. Some of the factors leading to placental abruption include:

• Trauma. An abdominal blow, such as that incurred during an automobile accident may cause abruption. Mothers experiencing a severe blow to the abdomen, with subsequent uterine contractions, should be monitored for about 24 hours, even in the absence of vaginal bleeding. This is because there could be a delay in symptoms. Observation of the mother should also include fetal monitoring to assure fetal well-being.

• Maternal hypertension. Mothers who have either chronic high blood pressure or hypertension induced by pregnancy are at increased risk of abruption.

• Maternal age. Placental abruption is seen more often in older women. However, it is unclear whether the advanced age or the increased likelihood of previous gestations is the primary factor.

• Uterine and umbilical cord abnormalities, such as a short cord or a uterine myoma at the placental implantation site.

• Placental abnormalities resulting in poor implantation.

• Cigarette smoking. As the number of cigarettes per day increases, so does the risk of abruption. This may be because of the harmful effect of nicotine on blood vessel integrity.

• Previous placental abruption. The risk of recurrence may be almost 17%.

The classic symptoms of abruption include sharp abdominal pain, rigid abdomen, vaginal bleeding, uterine contractions, and uterine tenderness. However, these signs are not always present. About 10% of women may have no vaginal bleeding. This is because the blood is pooling behind the placenta that has detached in the center. If the abruption occurred in tandem with labor contraction, and if the abruption is mild or moderate, the pain of labor contractions may mask the underlying abdominal pain and uterine tenderness of the abruption. This variability of symptoms emphasizes the need for careful diagnosis.

Diagnosis

Diagnosis of placental abruption, especially when mild or moderate, can be elusive. A thorough maternal history can play a significant role in identifying mothers at increased risk. Severity of abruption cannot be determined only from the volume of visible blood lost, as concealed hemorrhage may be taking place. Pain may be primarily in the back instead of abdominal. It may be sharp and severe, or dull and intermittent. It may be accompanied by nausea and vomiting. The uterine contraction pattern tends to be low in amplitude but high in frequency. If the uterus and abdomen are rigid, external monitoring or contractions may be inaccurate. Uterine tenderness may be localized to the site of detachment, but may also present as generalized. Unfortunately, ultrasound is not very reliable in establishing the presence of placental abruption. Blood work may be done to check on the presence of an abnormal clotting process. Diagnosis may become the piecing together of a puzzle of symptoms, with the experienced practitioner being more likely to solve the puzzle.

Placental abruption is categorized into four degrees of separation. These are:

• Grade 0. Abruption was diagnosed after delivery, upon inspection of the placenta. The placenta will show a small area of clotting on the side of maternal attachment. No other visible maternal or fetal signs of abruption were present.

• Grade 1. Some separation occurred with some vaginal bleeding and changes in maternal vital signs. No fetal distress was noted.

• Grade 2. Moderate separation, fetal distress, uterus is tender to touch.

• Grade 3. Extreme separation; without emergency intervention mother and fetus are at risk of shock, hemorrhage, or death.

Separation may be partial, with vaginal bleeding; partial without vaginal bleeding (known as concealed hemorrhage); complete separation, with vaginal bleeding (likely hemorrhage); or complete separation with concealed hemorrhage. Concealed bleeding is very dangerous because the lack of vaginal bleeding masks the true severity of the condition. Then, if the mother goes into shock, it may be unexpected and result in a poor outcome. If the placenta detached in the center, concealed bleeding is more likely to occur. Blood may seep into the uterine wall and result in a condition called couvelaire uterus, which is characterized by a hard uterus, no bleeding, and no signs of impending maternal shock. Shock results from the blood loss into the uterine tissue.

Treatment

A mother with suspected placental abruption needs to be admitted to the hospital. As complete a history as possible should be taken. If the mother is in crisis, family or friends may be able to assist with the history. Blood work to check for clotting disorders is done, as placental abruption may be accompanied by disseminated intravascular coagulation (DIC) which can lead to massive hemorrhage. Intravenous (IV) fluids and blood transfusions may be necessary to replace blood lost. Oxygen may be administered. Continuous fetal monitoring is done to assess for signs of fetal distress. Decreased maternal urine output indicates a compromised blood volume with poor tissue perfusion. The severity of the abruption determines the course of treatment. If a small separation has occurred, the pregnancy may be maintained as long as the mother is stable and the fetus does not show signs of distress. If the separation is a grade 0 or 1, and the fetus is near term, a vaginal delivery may be attempted. A separation of grade 3 or 4 necessitates delivery even if the fetus is not sufficiently mature, as the separation has compromised adequate nutrients and oxygen from reaching the fetus, and the accompanying blood lost has put the mother's well-being at risk. If DIC has begun, prompt evacuation of the uterus of the fetus and the placenta can allow for a positive prognosis for the mother. However, surgery poses great risk to the mother because of her compromised ability to clot. Severe hemorrhage, organ failure, and death could occur.

Prognosis

Prognosis is dependent on many factors such as the frequent monitoring of vital signs, the degree of separation, amount of blood lost, preexisting fetal complications such as growth retardation and congenital abnormalities, gestational age of the fetus, any permanent organ damage to the mother, and degree of oxygen deprivation. Prompt diagnosis enhances chances for a successful outcome.

Health care team roles

Nurses play a significant role in obtaining a full and accurate patient history. Questions should include maternal symptoms, time elapsed since symptoms began, presence and quality of pain (sharp, dull, constant, intermittent), bleeding (amount and color), and any actions taken, such as medication for pain or use of tampons.

Prevention

While most factors contributing to abruption are not preventable, cigarette smoking, cocaine use, and seat belt use with proper placement are important areas on which to focus during prenatal care. Identifying a mother at high risk and having a management plan in place can expedite diagnosis, especially if the mother arrives through the emergency department in crisis, and result in a more successful outcome for both mother and baby.

Key Terms

Disseminated intravascular coagulation

DIC is a serious medical complication in which the mother's blood no longer clots in the usual manner because of extreme loss of blood. Bruising is visible on the skin, and blood can seep from sites of IV insertion. This is a medical emergency, as it can quickly lead to massive hemorrhage.

Gestation

The age of the fetus in weeks since conception.

Myoma

A benign fibroid tumor of the uterine muscle.

Placenta previa

Placenta previa is a condition of pregnancy in which the placenta, which normally is implanted high on the uterine wall, is instead implanted near the cervical opening. As the uterus begins to change in preparation for labor and delivery, the force exerted on the placenta can cause it to tear, depriving the fetus of nutrition and oxygen, and putting the mother at risk of hemorrhage.