Obstetrics and Gynecology

Abruption

Placental abruption (abruptio placentae, premature separation of the placenta).

1. What every clinician should know

Key clinical features and incidence

In this condition, the placenta separates from the uterine wall prior to the birth of the fetus. The placenta is the source of oxygenation and nourishment to the fetus, and hence total or partial interruption of that supply puts the fetus in serious jeopardy. Abruption is an important cause of perinatal death and preterm delivery, as well as maternal morbidity and occasionally mortality.

The diagnosis of abruption is almost always a clinical one, based on recognition of symptoms and signs. It is important not to depend on test results to make or exclude the diagnosis of abruption. The clinical hallmarks of placental abruption are vaginal bleeding, abdominal pain, uterine contractions and fetal distress or death. Other features that may be present include maternal shock, disseminated intravascular coagulopathy and renal failure. There are two types of abruption: revealed, in which vaginal bleeding is obvious; and concealed, in which abruption occurs but there is no visible vaginal bleeding.

In concealed abruption, blood collects behind the placenta. Consumption of coagulation factors may lead to disseminated intravascular coagulopathy. Abnormal fetal heart rate patterns that may occur in abruption include fetal bradycardia, fetal heart rate decelerations, and a sinusoidal fetal heart rate pattern. Also, patients with abruption tend to have high frequency, low amplitude uterine contractions and hypertonus.

In cases of abruption affecting greater than 50% of the placenta, the fetus is often dead. The uterus may feel hard and tender and may assume the consistency of wood. Rarely, abruption may be found in asymptomatic patients at the time of ultrasound examination.

Placental abruption complicates approximately 1% of births. It appears that the rate of abruption is increasing in the United States. Abruption contributes to approximately 10% of preterm births and 10-20% of perinatal deaths.

Risk factors

Risk factors for abruption include hypertensive disorders of pregnancy, including preeclampsia and chronic hypertension. Other risk factors include smoking, cocaine use, prior cesarean delivery, uterine malformations, increasing maternal age and abdominal trauma. Abruption is known to recur; prior abruption is a strong risk factor for abruption, with recurrence rates ranging from 10-30%. Placental abruption may occur in association with polyhydramnios when sudden escape of amniotic fluid at the time of membrane rupture leads to shearing off of the placenta.

2. Diagnosis and differential diagnosis

A. Establishing the diagnosis

The diagnosis of placental abruption is mainly clinical. The diagnosis is typically made based on vaginal bleeding associated with abdominal pain, uterine tenderness, contractions, and sometimes a non-reassuring fetal heart rate tracing; however, abruption may be present in the absence of these symptoms. Absent fetal heart tones in a patient that presents with abdominal pain and/or bleeding is also very suspicious for placental abruption. When placental abruption occurs in a patient with a posteriorly located placenta, backache may be the only symptom.

A high index of suspicion is necessary to make the diagnosis, especially since the situation can deteriorate rapidly. Unfortunately, most laboratory tests are not helpful in diagnosing placenta abruption. Ultrasound has a low sensitivity for placental abruption. However, when abruption is suspected on the basis of sonographic findings, especially in the context of clinical features of abruption, the positive predictive value for abruption is extremely high. Some cases of placental abruption will be diagnosed incidentally in asymptomatic patients at the time of routine sonography.

Laboratory tests have little role in the diagnosis of placental abruption. However, tests to determine the degree of blood loss and of coagulopathy should be performed in all patients with a clinical suspicion of placental abruption. Tests for fetal-maternal hemorrhage, such as a Kleihauer-Betke test, are often performed in patients with suspected abruption. However, most patients with placental abruption will have negative K-B tests, and a positive K-B test may be found in pregnant women without abruption. Thus, this test cannot be depended on to make the diagnosis of abruption.

A complete blood count and a coagulation profile (activated plasma thromboplastin time, prothrombin time, international normalized ratio (INR) as well as a serum fibrinogen should be ordered in all patients with a suspicion of placental abruption.A simple bedside or operating room test for coagulopathy consists of putting blood in a red topped tube without anticoagulant and inverting the tube every minute. If there is no coagulopathy, a clot should form within 6-8 minutes. If no clot forms by 8 minutes, a presumptive diagnosis of coagulopathy can be made.

In the past, it was customary to test patients with placental abruption for inherited and acquired thrombophilias. Recent data do not show an increased risk for abruption among patients with thrombophilias; hence, screening patients with abruption for thrombophilias is no longer recommended. An ultrasound should be ordered in all patients with a suspicion of abruption. Sonography may help eliminate other causes, such as placenta previa or uterine fibroids, as the cause of the symptoms.

Similarly, tests such as urine microscopy and culture may help to rule in or rule out a urinary tract infection as the cause of the pain. Rarely, an amniocentesis may be performed if there is a suspicion that intraamniotic infection may be responsible for the patient's symptoms. Continuous fetal heart rate monitoring should be instituted. Fetal heart rate abnormalities may help in making the diagnosis of abruption.

Sonographic findings that are highly suggestive of abruption include a retroplacental clot that is echolucent or echogenic behind the placenta. There may also be a thickened, heterogenous placenta. Other findings include blood clot floating freely in the amniotic fluid; a thickened heterogenous placenta; an echolucent area adjacent to the placental edge, representing a subchorionic hematoma with chorioamniotic separation (Figure 1); or blood in the preplacental region. The appearance depends on the amount of time since the abruption. Initial findings may be echolucent, gradually becoming echodense with time.

Figure 1.

Sonogram showing placental abruption. The subchorionic marginal hematoma (arrows) is seen. Blood tracked along the membranes from the edge of the placenta, forming this echolucent hematoma with mixed echos. The placenta is labelled "P".

While it is customary to diagnose abruption after delivery by the presence of a clot attached to the placenta (Figure 2), it is important to realize that sudden, severe abruption may not result in a clot, especially when the fetus is delivered soon after the abruption. Also the presence of a clot attached to the placenta after delivery may not by itself represent a placental abruption. In a normal delivery, when delivery of the placenta is delayed, clots may form behind the placenta, even though there was no abruption.

Figure 2.

Placenta after delivery showing a large clot (c). This massive abruption led to death of the fetus at 34 weeks of gestation.

In all cases where an abruption is suspected, the placenta should be sent for pathology examination. Pathologists may make the diagnosis of abruption in otherwise totally uncomplicated deliveries. It should be emphasized that abruption is, for the most part, a clinical diagnosis.

B. Other possible diagnoses

The differential diagnosis includes other causes of bleeding and abdominal pain in pregnancy. Perhaps the other most common cause of bleeding is placenta previa, a placenta that is abnormally located in the lower uterine segment, covering, or in close proximity to, the internal cervical os. The bleeding that occurs with placenta previa is typically painless, as opposed the painful bleeding that occurs with abruption. Other differential diagnoses include uterine fibroids, chorioamnionitis, appendicitis, urinary tract infection, ovarian torsion and preterm labor.

It is important to realize that any of these conditions may co-exist with abruption. Other symptoms and signs such as dysuria and frequency, fever, nausea and vomiting may help differentiate between these conditions. Ultrasound, blood work, and sometimes a CT scan and a surgery consultation (in cases of suspected appendicitis), may be helpful in making the differential diagnosis. A digital cervical examination may show a dilated cervix indicating preterm labor; however, preterm labor may co-exist with abruption.

3. Management

Antepartum

Management of abruption depends on the severity of the abruption and gestational age, as well as stability of the mother and fetus. Treatment should be individualized, based on each patient's unique circumstances, rather than using a "cookbook" approach. In cases in which fetal death has occured, the mother should be delivered, with vaginal delivery the preferred route. Often, the patient is already in labor, and forewater amniotomy leads to rapid delivery.

When abruption occurs at term or near term (more than 34 weeks of gestation), delivery is the best option, even when the fetus and mother are stable. At earlier gestations, the management depends on the severity of the abruption as well as the risk of prematurity. In selected cases in which both fetal and maternal statuses are reassuring, conservative management may be employed, with the goal of achieving a greater gestational age at delivery. However, the risk of fetal death is very high, and conservative management should be abandoned when there is fetal or maternal compromise.

All patients with suspected placental abruption of any degree should be admitted to hospital for evaluation. Intravenous access should be instituted. Close fetal monitoring should be performed. If a significant abruption occurs prior to 24 weeks of gestation, the prognosis is bleak, especially if there is associated oligohydramnios, and the option of termination of pregnancy should be discussed. If the gestational age is more than 24 weeks, continuous fetal monitoring should be employed, at least for the first 24 hours. Maternal corticosteroids should be administered between 24 and 34 weeks of gestation to promote fetal lung maturation, since these pregnancies will almost certainly be delivered preterm. Rh-Immune globulin should be administered to patients who are Rh-negative.

In cases where the fetal and maternal status are reassuring and there has been no bleeding, abdominal pain or contractions for more than 48 hours, consideration may be given to outpatient management. The patient should be compliant and have quick access to hospital. The patient should be aware that sudden complete placental abruption may occur that may result in fetal death. In cases of abruption diagnosed prenatally and managed conservatively, elective delivery at 37-38 weeks is reasonable, since a risk for sudden placental separation and fetal death is always present.

A special note should be made of patients who have had abdominal trauma in pregnancy. This may be direct trauma, such as that sustained from a direct kick or blow to the abdomen, or indirect trauma, such as acceleration/deceleration that can occur during a motor vehicle accident in a restrained passenger. Shearing forces may lead to placental separation. Abruption may not be obvious immediately. Not infrequently, these patients do not have bleeding or abdominal pain, only to present with abruption 2-3 days later.

Pregnant women who sustain abdominal trauma should be monitored for at least 4 hours. If there is no bleeding, abdominal pain or contractions, they may be discharged home. Contractions may be an early sign of abruption. Hence, if these women are contracting, prolonged fetal monitoring of at least 8-12 hours should be performed.

Intrapartum

Vaginal delivery is the preferred mode of delivery, especially when the fetal status is reassuring. However, cesarean delivery may be necessary when there are contraindications to vaginal delivery, when labor does not progress, or when fetal or maternal status mandates a need for rapid delivery. Continuous fetal monitoring should be employed during labor, with a low threshold for operative delivery in any case of suspected abruption. If there is any sign of non-reassuring fetal status, prompt delivery by cesarean is indicated.

The patient should have at least one wide bore intravenous cannula inserted. Blood should be taken for complete blood count, type and screen and coagulation studies. Blood loss and intravascular volume depletion should be replaced promptly and adequately. Coagulopathy should be corrected. This will often involve administration of fresh frozen plasma (FFP). Sometimes cryoprecipitate and platelets also may need to be administered. Close communication with the blood bank is essential. In cases where there is coagulopathy and cesarean delivery is to be undertaken, aggressive correction of coagulopathy using fresh frozen plasma and/or cryoprecipitate as required should be performed as the patient is prepared for surgery.

Postpartum

It is important to ensure that blood loss is controlled and that any coagulopathy is corrected. In severe cases of abruption, a Foley catheter may be necessary to closely monitor urine output. Blood and blood products should be replaced as needed. It may be necessary to admit the patient to the intensive care unit.

4. Complications

Fetal death may occur, especially when more than 50% of the placenta separates from the uterine wall. Preterm delivery frequently occurs with placental abruption. Maternal complications include severe hemorrhage with hypovolemic shock. Disseminated intravascular coagulopathy may occur due to consumption of clotting factors. In severe cases, the patient may develop acute renal failure due to acute tubular necrosis or acute cortical necrosis.

The key to minimizing the risk of complications is early recognition of the abruption and appropriate management. For instance, a high index of suspicion for abruption and prompt delivery by cesarean may prevent fetal death and may also reduce the risk for perinatal asphyxia. Early recognition of impending coagulopathy, and treatment with blood transfusion and clotting factors may prevent severe coagulopathy with the associated severe maternal morbidity. Conservative management of severe preeclampsia remote from term carries a significant risk for placental abruption. If these cases are managed conservatively, close fetal monitoring should be performed. Prompt delivery should occur if there are any symptoms or signs suspicious for abruption.

5. Prognosis and outcome

A. Maternal and fetal/neonatal outcomes

The fetal prognosis depends on the gestational age and the degree of placental separation. In cases in which more than 50% of the placenta separates, most fetuses die. Fetuses that are born preterm may suffer from the consequences of prematurity, including perinatal death, respiratory distress syndrome, necrotizing enterocolitis and long term neuro-developmental handicap. In addition, the newborn may be exposed to ischemia and hypoxia, and may develop hypoxic-ischemic encephalopathy, with long term neurodevelopmental sequelae.

The long term maternal prognosis depends on the amount of hemorrhage, the presence of coagulopathy, the presence of renal compromise and the rapidity with which the abruption and its complications are treated. In the worst cases, maternal death may occur. Fortunately, in the Western world, this is exceedingly rare. In cases of severe hemorrhagic shock with disseminated intravascular coagulopathy, hysterectomy may be necessary. Patients may need to be intubated and admitted to the intensive care unit.

B. Long term maternal health

Patients who have an abruption have a recurrence risk of approximately 15% in subsequent pregnancies. In addition, these patients have an increased risk for preeclampsia and growth restriction in subsequent pregnancies. No other long term health risks have been found in patients who have abruption and recover completely from complications of the abruption.

6. What is the evidence for specific management and treatment recommendations

Pariente, G, Wiznitzer, A, Sergienko, R, Mazor, M, Holcberg, G. "Placental abruption: Critical analysis of risk factors and perinatal outcomes". J Matern Fetal Neonatal Med. vol. 24. 2011. pp. 698-702.

(This epidemiologic population based study of 185,476 pregnancies from Israel examined risk factors for abruption. The authors found hypertensive disorders, prior cesarean delivery, and maternal age to be risk factors for abruption. They also found that abruption was associated with perinatal mortality and low Apgar scores.)

Getahun, D, Oyelese, Y, Salihu, HM, Ananth, CV. "Previous cesarean delivery and risks of placenta previa and placental abruption". Obstet Gynecol. vol. 107. 2006. pp. 771-8.

(This population based study found an increased risk of abruption in patients in their second pregnancies with a prior cesarean delivery when compared with women who had a vaginal first birth.)

Tikkanen, M, Nuutila, M, Hillesmaa, V, Paavonen, J, Ylikorala, O. "Prepregnancy risk factors for placental abruption". Acta Obstet Gynecol Scand. vol. 85. 2006. pp. 40-4.

(This study found that smoking, uterine malformations, previous cesarean delivery and a history of abruption were risk factors for abruption.)

Toivonen, S, Heinonen, S, Anttila, M, Kosma, VM, Saarikoski, S. "Obstetric prognosis after placental abruption". Fetal Diagn Ther. vol. 19. 2004. pp. 336-41.

(This population based study from Scandinavia found the recurrence rate of placental abruption to be 11%. The odds ratio of abruption in a subsequent pregnancy was 16.9 (95% CI: 8.2-34.9) when compared with the general population. Patients with an abruption also had an increased risk for preeclampsia in a subsequent pregnancy.)
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