Abruptio Placentae

Premature Separation of the Placenta (Abruptio Placentae, Marginal Sinus Bleed

Essentials of Diagnosis

• Unremitting abdominal (uterine) or back pain.
• Irritable, tender, and often hypertonic uterus.
• Visible or concealed hemorrhage.
• Evidence of fetal distress may or may not be present, depending on the severity of the process.

General Considerations

Premature separation of the placenta is defined as separation from the site of uterine implantation before delivery of the fetus

The term premature separation of the normally implanted placenta is most descriptive because it differentiates the placenta that separates prematurely but that is implanted some distance beyond the cervical internal os from one that is implanted over the cervical internal os—that is, placenta previa. This is cumbersome, however, and hence a shorter term abruptio placenta, or placental abruption, has been used. The Latin abruptio placentae, which means "rending asunder of the placenta," denotes a sudden accident, a clinical characteristic of most cases of this complication.

Two principal forms of premature separation of the placenta can be recognized, depending on whether the resulting hemorrhage is external or concealed

Concealed form

Less often, the blood does not escape externally but is retained between the detached placenta and the uterus, leading to concealed hemorrhage

Detachment of the placenta may be complete, and the complications often are severe. Approximately 10% of abruptions are associated with clinically significant coagulopathies (disseminated intravascular coagulation [DIC]), but 40% of those severe enough to cause fetal death are associated with coagulopathy

External form

Some of the bleeding of placental abruption usually insinuates itself between the membranes and uterus, and then escapes through the cervix, causing external hemorrhage

Placental detachment is more likely to be incomplete, and the complications are fewer and less severe. Occasionally, the placental detachment involves only the margin or placental rim. Here, the most important complication is the possibility of premature labor.

Etiology

The hypertensive states of pregnancy are associated with 2.5–17.9% incidence of placental separation

Other predisposing factors include advanced maternal age, multiparity, uterine distention (e.g., multiple gestation, hydramnios), vascular disease (e.g., diabetes mellitus, systemic lupus erythematosus), thrombophilias, uterine anomalies or tumors (e.g., leiomyoma), cigarette smoking, alcohol consumption (> 14 drinks per week), cocaine use, and possibly maternal type O blood.

Risk Factors for Placental Abruption

Risk Factor Increased age and parity Preeclampsia Chronic hypertension Preterm ruptured membranes Multifetal gestation Hydramnios Cigarette smoking Thrombophilias Cocaine use Prior abruption Uterine leiomyoma

Pathophysiology & Pathology

Several mechanisms are thought to be important in the pathophysiology of premature placental separation. One mechanism is local vascular injury that results in vascular rupture into the decidua basalis, bleeding, and hematoma formation. The hematoma shears off adjacent denuded vessels, producing further bleeding and enlargement of the area of separation.

Another mechanism is initiated by an abrupt rise in uterine venous pressure transmitted to the intervillous space. This results in engorgement of the venous bed and separation of all or a portion of the placenta.

Conditions predisposing to vascular injury and known to be associated with an increased incidence of placental separation are preeclampsia–eclampsia, chronic hypertension, diabetes mellitus, chronic renal disease, cigarette smoking, and cocaine use.

Retained or concealed hemorrhage is likely when:

1.      There is an effusion of blood behind the placenta but its margins still remain adherent.

2.      The placenta is completely separated yet the membranes retain their attachment to the uterine wall.

3.      Blood gains access to the amnionic cavity after breaking through the membranes.

4.      The fetal head is so closely applied to the lower uterine segment that the blood cannot make its way past it.

Clinical Findings

Signs and Symptoms in patients with abruptio placentae

Sign or Symptom Vaginal bleeding Uterine tenderness or back pain Fetal distress Preterm labor a   High-frequency contractions Hypertonus Dead fetus

Differential Diagnosis

With severe placental abruption, the diagnosis generally is obvious. Milder and more common forms of abruption are difficult to recognize with certainty, and the diagnosis is often made by exclusion. Unfortunately, neither laboratory tests nor diagnostic methods are available to detect lesser degrees of placental separation accurately. Therefore, with vaginal bleeding complicating a viable pregnancy, it often becomes necessary to rule out placenta previa and other causes of bleeding by clinical inspection and ultrasound evaluation. It has long been taught, perhaps with some justification, that painful uterine bleeding means placental abruption, whereas painless uterine bleeding is indicative of placenta previa. Unfortunately, the differential diagnosis is not that simple. Labor accompanying placenta previa may cause pain suggestive of placental abruption. On the other hand, abruption may mimic normal labor, or it may cause no pain at all. The latter is more likely with a posteriorly implanted placenta. At times, the cause of the vaginal bleeding remains obscure even after delivery.

Management

Expectant Management in Preterm Pregnancy

Delaying delivery may prove beneficial when the fetus is immature, but it is exceptional, not rule. This management pathway should be attempted only with careful observation of the patient and a clear clinical picture. In general, expectant management may be appropriate when the mother is stable, the fetus is immature, and the fetal heart tracing is reassuring. The patient should be observed in the labor and delivery suite for 24–48 hours to ensure that further placental separation is not occurring. Continuous fetal and uterine monitoring should be maintained. Changes in fetal status may be the earliest indication of an expanding abruption.

Emergency Measures

Most cases of placental abruption are diagnosed as an acute event (upon presentation to labor and delivery or during the intrapartum period), making immediate intervention necessary. If the patient exhibits clinical findings that become progressively more severe or if a major placental separation is suspected as manifested by hemorrhage, uterine spasm, or fetal distress, an acute emergency exists.

Blood should be drawn for laboratory studies and at least 4 units of PRBCs typed and crossed. Two large-bore intravenous catheters should be placed and crystalloid administered.

Otherwise delivery should be considered either with caesarian section or vaginal delivery as patient’s condition and pregnancy allows.

 Vaginal Delivery

An attempt at vaginal delivery is indicated if the degree of separation appears to be limited and if the continuous FHR tracing is reassuring. When placental separation is extensive but the fetus is dead or of dubious viability, vaginal delivery is indicated. The exception to vaginal delivery is the patient in whom hemorrhage is uncontrollable and operative delivery is necessary to save the life of the fetus or mother.

Induction of labor with an oxytocin infusion should be instituted if active labor does not begin shortly after amniotomy. In practice, augmentation often is not needed because usually the uterus is already excessively irritable. If the uterus is extremely spastic, uterine contractions cannot be clearly identified unless an internal monitor is used, and the progress of labor must be judged by observing cervical dilatation. Pudendal block anesthesia is recommended. Conduction anesthesia is to be avoided in the face of significant hemorrhage because profound, persistent hypotension may result. However, in the volume-repleted patient in early labor, a preemptive epidural should be considered because rapid deterioration of maternal or fetal status can occur as labor progresses.

Cesarean Section

The indications for cesarean section are both fetal and maternal. Abdominal delivery should be selected whenever delivery is not imminent for a fetus with a reasonable chance of survival who exhibits persistent evidence of distress. Cesarean section also is indicated if the fetus is in good condition but the situation is not favorable for rapid delivery in the face of progressive or severe placental separation. This includes most nulliparous patients with less than 3–4 cm of cervical dilatation. Maternal indications for cesarean section are uncontrollable hemorrhage from a contracting uterus, rapidly expanding uterus with concealed hemorrhage (with or without a live fetus) when delivery is not imminent, uterine apoplexy as manifested by hemorrhage with secondary relaxation of a previously spastic uterus, or refractory uterus with delivery necessary (20%).

Complications

Disseminated Intravascular Coagulation

Placental abruption can lead to initiation of the coagulation cascade by release of tissue thromboplastin into the maternal circulation. Consumption of coagulation factors and platelets is followed by coagulopathic hemorrhage. A cycle ensues as further bleeding worsens the depletion of coagulation factors. Continuous monitoring for evidence of a clotting deficiency is mandatory from the time the diagnosis of placental abruption is considered well into the postpartum period. Treatment will depend not only on the demonstration of hematologic deficiencies but also on the amount of active bleeding and the anticipated route of delivery.

Reference

Tenth edition of Current Diagnosis & Treatment Obstetrics & Gynecology.

Twenty second edition Williams Obstetrics