Moss H. Mendelson
Vaginal bleeding after 20 weeks’ gestation is not uncommon and can be frightening to the patient as well as to the physician. Definitive treatment, if required, should be performed by an obstetrician. The emergency physician must stabilize the patient hemodynamically and should be aware of the differential diagnosis, the studies necessary to define the problem, as well as the indications for transfer if limited facilities exist for management of the mother or the premature or distressed newborn.
Placental abruption (abruptio placentae), premature separation of part of the placenta from the uterine wall, complicates 1% to 2% of all pregnancies. Risk factors include hypertension and maternal tobacco and cocaine use. In addition, abdominal trauma with transmission of forces to the uterus can cause shearing of the placenta from its attachments (1).
Placenta previa, which accounts for about 20% of third-trimester bleeding, is a placenta that overlaps the cervix to varying degrees. Placenta previa is more common with a uterus scarred from previous cesarean section and with advanced maternal age. Of placentas that overlie the cervix before 20 weeks’ gestation (approximately 5% of pregnancies), <10% remain so at delivery (2). The other 50% of patients who experience late bleeding often have no definite cause identified. It is believed that most episodes of bleeding represent small marginal separations of the placenta, but this cannot usually be proven. Other causes of bleeding in later pregnancy include vaginal or cervical trauma, lower genital tract infections, polyps, or hemorrhoids.
The alterations in maternal cardiovascular physiology that occur during pregnancy affect evaluation and management, as well as the clinical course of disease. Maternal blood volume expands by about 1.5 L during a normal pregnancy, resulting in a dilutional anemia that is physiologic (hematocrit 32% to 34%). Pregnant patients also manifest a baseline increase in heart rate (90 to 100 beats/min) and stroke volume, resulting in a cardiac output 30% to 40% higher at term than seen in the nonpregnant state. Systematic vascular resistance is decreased, however, and the net hemodynamic result of these changes is a blood pressure lower than that in the nonpregnant state. Finally, the uteroplacental bed does not have any autoregulatory function; placental blood flow is determined strictly by maternal blood pressure and cardiac output. Because of expanded maternal intravascular volume, signs of extensive blood loss can occur late, and significant fetal hypoperfusion can develop before maternal signs of shock are apparent. Pregnancy is also associated with a rise in concentration of many clotting factors (especially fibrinogen), resulting in a hypercoagulable state.
CLINICAL PRESENTATION
The patient with bleeding after 20 weeks’ gestation may present with a spectrum of signs and symptoms ranging from painless spotting or bloody mucoid discharge to dark or exsanguinating bleeding and severe uterine pain. Placenta previa most often presents as bright red, painless vaginal spotting. The bleeding is rarely severe (except during labor or after pelvic examination with probing of the cervical os). The patient may already be aware of an abnormal placental location. The patient with placental abruption more often has dark, variable bleeding accompanied by uterine tenderness and irritability, manifested by intermittent or steady cramping. Bleeding between the placenta and uterine wall may result in significant occult blood loss, with maternal and fetal compromise, but without evidence of significant external bleeding. Fetal distress (heart rate out of the normal range of 120 to 160 beats/min) can occur if a significant degree of separation has occurred. Abruption may also trigger maternal coagulation, thereby resulting in evidence of consumptive coagulopathy, with bleeding from needlesticks, urine, and other sites.
DIFFERENTIAL DIAGNOSIS
The main disorders that must be considered in the pregnant patient with vaginal bleeding are placental abruption and placenta previa. Other possibilities include bleeding from a cervical or vaginal lesion or from a nonvaginal source such as genitourinary (cystitis, urethritis, and nephrolithiasis) or gastrointestinal (hemorrhoids, polyp, and ulcer).
ED EVALUATION
The patient with vaginal bleeding should first be assessed hemodynamically. With significant maternal blood loss, fluid resuscitation should be initiated during the initial evaluation. Blood should be sent for complete blood cell count, prothrombin time, partial thromboplastin time, and fibrinogen levels. The patient’s blood should be typed and crossmatched, as blood transfusion may be necessary. The mother’s Rh type should be determined and a Kleihauer–Betke test sent to determine whether significant fetomaternal transfusion has occurred (3). Continuous fetal monitoring should be established as quickly as possible in these high-risk patients, so as to identify signs of fetal distress. Bradycardia <120 beats/min, tachycardia >160 beats/min, decelerations, and loss of beat-to-beat variability all can indicate fetal hypoxemia and acidosis, with an increased risk of fetal demise.
History should include known obstetric problems and ultrasonographic diagnoses. Other historical information includes amount of bleeding, passage of clots, character of blood (bright red or dark, older blood), presence of uterine cramping or pain, prior cervical or vaginal lesions or infection, drug use, and history or evidence of abdominal trauma (including domestic violence).
The initial focus of the physical examination should be to determine whether the patient is severely hypovolemic, whether the bleeding is in fact vaginal (as opposed to urinary or rectal), and whether delivery is in progress. Abdominal examination should confirm uterine size as well as the presence of contractions or tenderness to palpation. Though an external inspection is appropriate, vaginal examination should not be performed in the ED because it may precipitate severe hemorrhage and fetal compromise.
Ultrasonography is the diagnostic modality of choice for late pregnancy bleeding. The major purpose of ultrasonography is to locate the placenta and define its relationship to the cervix. In addition, information regarding gestational age and general fetal well-being may be obtained. Transabdominal ultrasound (TAS) is usually performed first but is noted to have a false-positive rate of 2% to 6% for placenta previa. False-positives can be caused by obesity, a posterior placenta, a full bladder, or a focal myometrial contraction. Endovaginal sonography (EVS) eliminates many of these false-positives and has been proven safe in many studies. Although TAS is easily performed in the ED and may yield helpful information, EVS should not be done in the ED in patients with third-trimester vaginal bleeding (1,4).
On the other hand, ultrasonography is insensitive for abruption. Findings in abruption are variable and are affected by the type of abruption (retroplacental or subchorionic) and the timing of the study in relationship to the onset of bleeding. Retroplacental bleeding may have a sonographic appearance very similar to that of a normal placenta, creating an area of thickened placenta or an area mistaken for a fibroid or contraction. Marginal bleeding may be recognized sonographically as a hematoma, although the amount of blood identified on ultrasound may significantly underestimate true losses. Evidence of abruption by ultrasound is helpful to the obstetrician in developing a care plan for the patient and can be followed up with serial examinations. A negative study does not eliminate abruption from the differential and, in fact, a patient with late pregnancy bleeding and an ultrasound negative for placenta previa is often assumed to have abruption. With abruption, fetal monitoring becomes the primary tool for management decisions (1,5).
A vaginal examination is ideally performed after ultrasonography, by the obstetrician, in an operating suite capable of rapid surgical delivery with fetal resuscitation, in the event that severe bleeding is triggered. If immediate obstetric consultation is not available, patients with significant bleeding should be prepared for transport to a facility that is able to provide appropriate obstetric and neonatal services. In this situation, if the bleeding is not severe, a cautious vaginal examination in the ED is reasonable, after placenta previa has been excluded with transabdominal ultrasonography. The purpose of the examination is to exclude vaginal or cervical lesions that cause bleeding. Neither fingers nor instruments should be placed in the cervical os, because uncontrolled bleeding from a placenta previa can be triggered by such manipulation.
KEY TESTING
• Transabdominal ultrasonography to locate the placenta and obtain an overview of fetal age and status
• Fetal Monitoring should be initiated early
• Type and screen, CBC, PT, PTT, and fibrinogen level
ED MANAGEMENT
Prehospital triage of the woman with bleeding after 24 weeks of gestation (as estimated by the uterus being palpable above the umbilicus) should be to a facility that can manage a potentially high risk or premature delivery. The prehospital management should consist of assessment of the amount of bleeding from evidence at the scene and the degree of current perineal bleeding, administration of maternal supplemental oxygen, positioning of the patient on her left side, and intravenous administration of fluids en route.
For patients with late pregnancy vaginal bleeding, the ED should ideally be a place of cardiovascular stabilization and triage only; there is a paucity of evidence in this area, and case-by-case decision making by the obstetrics team is mandatory. If there is hemodynamic compromise secondary to hemorrhage, fluid resuscitation should be initiated rapidly with crystalloid. In the mother with rapid exsanguination, O-negative blood and the use of massive transfusion protocols may be required. In cases of severe bleeding, especially with abruption, disseminated intravascular coagulation (DIC) should be anticipated. The blood bank should be notified of the potential need for fresh frozen plasma and platelets. Fetal heart rate should be quickly measured, with initiation of continuous monitoring if possible. Rapid transport to the obstetric suite is the goal (1,2,5).
In the patient with less emergent bleeding, referral to the obstetric unit is preferred for definitive diagnosis. The standard method of evaluation is ultrasonography followed by vaginal examination in a delivery suite, where the discovery of a fetus-threatening placenta previa can be treated with rapid delivery. In the patient with presumed or visible abruption, admission to a high-risk prepartum unit for continuous monitoring is appropriate. Continued fetal well-being should always be documented if the patient spends any significant time in the ED, because hypovolemia is frequently detected by signs of fetal distress before there are changes in the mother’s vital signs. If the mother is Rh-negative (with an unknown or Rh-positive father) or if a Kleihauer–Betke test is positive for fetomaternal hemorrhage, RhoGAM should be administered. If fetomaternal hemorrhage in excess of 15 mL of fetal RBCs has occurred, additional RhoGAM may be necessary (consider 10 μg for every additional 0.5 mL fetal RBCs) (3).
CRITICAL INTERVENTIONS
• Do not perform an internal vaginal examination in the ED for third-trimester pregnant patients with vaginal bleeding.
• Provide aggressive volume resuscitation as appropriate. Anticipate the need for massive transfusion and DIC in patients with severe bleeding.
• Immediately consult an obstetrician or arrange transfer to a suitable facility if necessary.
DISPOSITION
All patients with late pregnancy vaginal bleeding require obstetric consultation. The only exception is the patient who is discovered to have bleeding from a nonvaginal source, such as an external hemorrhoid. If necessary, interfacility transfer to a high-risk unit should be accomplished after initial diagnosis or assessment by an obstetrician and is usually performed by specialized obstetric or high-risk neonatal transport units. In general, predelivery transport is safest and is associated with the best outcome, but it must be accomplished in a controlled fashion, with personnel capable of supporting the mother and managing fetal distress or a premature delivery en route.
Common Pitfalls
• Vaginal examinations should be limited to visual inspection of the perineum to look for obvious nonuterine bleeding sources. Fingers or instruments should never be placed in or near the cervix, as uncontrolled bleeding from a placenta previa can result.
• Coagulopathy should be considered in patients with severe hemorrhage, as clotting factors are consumed when significant bleeding occurs with abruption, and coagulopathy can seriously compromise the mother’s ability to limit uterine bleeding.
REFERENCES
1. Oyelese Y, Ananth CV. Placental abruption. Obstet Gynecol. 2006;108:1005–1016.
2. Neilson JP. Interventions for suspected placenta praevia (Review). The Cochrane Collaboration. JohnWiley & Sons, Ltd., 2003.
3. Fung Kee Fung K, Eason E, Crane J, et al. Prevention of Rh alloimmunization. J Obstet Gynaecol Can. 2003;25:765–773.
4. Moore C, Promes SB. Ultrasound in pregnancy. Emerg Med Clin North Am. 2004;22:697–722.
5. Neilson JP. Interventions for treating placental abruption. Cochrane Database of Syst. Rev. 2003, Issue 1. Art. No.: CD003247. DOI:10.1002/14651858.CD003247.