Placental Abruption

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Diagnosis and reasoning

This lady has presented with an antepartum hemorrhage. Although the vaginal bleeding appears mild, she is pale, tachycardic and has a borderline hypotensive blood pressure - all of which suggest significant concealed bleeding. Very few diseases give rise to this degree of bleeding - mainly placental abruption or placenta previa. While vasa previa may cause severe bleeding, the blood loss is from the baby - the mother would not become hemodynamically unstable. Placenta previa is unlikely, as the bleeding is usually painless, while the uterus is typically soft and non-tender. In addition, the degree of hemodynamic compensation is usually proportionate to the severity of the vaginal bleeding. Placental abruption is highly likely, as these patients usually present with abdominal pain and a tender and contracted uterus (due to uterine irritation following exposure to blood). Often, the bleeding may be mostly concealed, with hemodynamic decompensation disproportionate to the degree of vaginal bleeding (as in this patient). Note that up to 15% of placenta previas may be associated with simultaneous abruption - thus these diagnoses are not mutually exclusive. Pelvic ultrasound shows a placenta located in the upper segment of the uterus (which excludes placenta previa). Note also that the lack of sonographic findings suggestive of abruption or a concealed hemorrhage does not exclude placental abruption, as ultrasound is not sensitive in this regard. Cardiotocography shows reduced variability of the fetal heart rate, which is suggestive of utero-placental insufficiency. Her full blood count shows marked anemia, supporting the clinical suspicion of hemorrhage. Note that when assessing the severity of bleeding, the clinical presentation takes precedence over the hemoglobin level measurement, as the latter may take several hours to change. This is because, in acute bleeding, the total volume of blood is decreased - but the hemoglobin level per unit of blood remains stable initially. Her coagulation screen excludes a coagulapathy (which occurs in up to 30% of patients with abruption). As there is both maternal hemodynamic compromise and fetal distress, her immediate management should consist of resuscitation and blood transfusion, followed by urgent delivery via cesarian section. Antenal corticosteroids are known to accelerate fetal pulmonary maturity. While they ideally require 24 to 48 hours to achieve maximum effectiveness, the baby may still derive some benefit from them, even in an urgent delivery. Even though she has received anti-D immunoglobulin for routine antenatal prophylaxis, she has experienced a sensitizing event and (in accordance to current guidelines) requires an additional dose of anti-D immunoglobulin. The exact dose may be determined via either flow cytometry or a Kleihauer screening test.


Discussion

Placental abruption is defined as a premature separation of the placenta from the uterus, and complicates approximately 1% of deliveries. While the exact pathophysiology is unclear, it is known that abruption results from hemorrhage at the decidual-placental interface. This may be secondary to both acute causes (i.e. trauma), or as a consequence of long-standing processes (i.e. hypertensive disorders). The acute separation of the placenta deprives the fetus of oxygen and nourishment, causing fetal distress and subsequently death. In addition, the coagulation cascade is often activated, causing a consumptive coagulopathy and worsening the hemorrhage. Risk factors include hypertensive disorders, tobacco and cocaine use, multiple pregnancies, polyhydramnios, preterm premature rupture of membranes, and trauma. While the classical presentation of abruption is vaginal bleeding associated with abdominal pain, patients may present with only one or neither of these symptoms. Note that the severity of vaginal bleeding does not correlate with the degree of abruption, as the hemorrhage may be partially or fully concealed. Backache may be present and be the only symptom, especially if the placenta is located posteriorly. Examination typically shows a tender, hard uterus, although this is not universally present. If bleeding occurs into the uterine myometrium, a beefy boggy uterus, called a Couvelaire uterus may be palpated. Auscultation may show fetal bradycardia due to fetal distress, or absent fetal heart sounds if fetal demise has occurred. Note that digital vaginal examination should never be performed in patients with an antepartum hemorrhage until a placenta previa has been excluded, as torrential bleeding may be provoked otherwise. Abruption is primarily a clinical diagnosis, although investigations may provide important supporting evidence. The sonographic appearance of abruption is highly variable, and may range from a hypoechoic area between the placenta and uterus, to a preplacental collection beneath the chorionic plate, amniotic fluid and placenta, or merely a thickened placenta with a heterogenous appearance. In many cases, there may be no abnormal findings. Another important role of ultrasonography lies in determination of the placental location. If there is a placenta previa, it is unlikely that abruption is the cause of the bleeding. Note that a clot over the cervix may be mistaken for placenta previa. The sensitivity and specificity of ultrasound for the diagnosis of abruption is reported to be 24% and 96% respectively. While the Kleihauer-Betke test is frequently performed when abruption is suspected, studies have shown that a negative test does not rule out abruption, nor does a positive test confirm abruption. However, the test allows quantification of feto-maternal transfusion to guide dosing of anti-D immune globulin in Rh-negative patients. Cardiotocography may show recurrent late or variable decelerations or bradycardia, indicating fetal distress, or a sinusoidal fetal heart rate pattern, which is suggestive of imminent fetal demise. The initial management of abruption includes acute resuscitation, close maternal and fetal monitoring, IV access, grouping and cross-matching of blood and performance of an urgent full blood count and coagulation profile (including serum fibrinogen levels). In general, the presence of maternal instability or fetal distress necessitates urgent delivery, while if both mother and fetus are stable, the timing of delivery will depend on the gestational age, degree of maternal and fetal compromise and stage of labor. Following delivery, if no obvious underlying cause for the abruption is identifiable, thrombophilia screening should be considered. In addition, these patients should be closely monitored in subsequent pregnancies as they are at a ten-fold increased risk of abruption.


Take home messages

  1. Placenta previa and placental abruption are the most common causes of severe antepartum hemorrhage.
  2. The bleeding in placental abruption may be mostly concealed, leading to hemodynamic decompensation disproportionate to the degree of vaginal bleeding.
  3. Digital vaginal examination should be avoided in patients with antepartum hemorrhage until placenta previa has been excluded.
  4. Pelvic ultrasonography has a poor sensitivity for the detection of abruption and concealed hemorrhage.
  5. The clinical presentation takes precedence over the hemoglobin level when assessing the degree of hemorrhage.
  6. The ultimate management of abruption depends on the maternal and fetal status, duration of pregnancy and stage of labor.

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  1. AFP : Late Pregnancy Bleeding (2007)
  2. British Journal of Anesthesia : Maternal haemorrhage (2009)
  3. Journal of Obstetrics and Gynecology : Ante-partum haemorrhage: An update (2008)
  4. Obstetrical and Gynecological survey : Placental Abruption (2002)
  5. Obstetrics and Gynecology : Placental Abruption (2006)
  6. RCOG : The Use of Anti-D Immunoglobulin for Rhesus D Prophylaxis (2011)