Special Feature
Third Trimester Vaginal Bleeding
By Glenn C. Freas, MD, JD, FACEP
When a patient presents to the emergency department (ED) with third trimester vaginal bleeding, the emergency physician is presented with a unique challenge. By virtue of the patient’s presence in the ED, she is either too unstable to go directly to the labor and delivery suite in the hospital, or the hospital has no labor and delivery capabilities. The emergency physician must rapidly make decisions based upon limited information (the inability to safely do a vaginal exam in most cases), the stability of mother and fetus, and the resources available in the hospital.
This article will review the two most serious identifiable causes of bleeding in late pregnancy, placenta previa (PP), and placental abruption (PA). Both of these conditions can occur in the second trimester of pregnancy, as well as in the third trimester. Each can threaten fetal viability and cause significant maternal morbidity, as well as mortality. Incidence, epidemiology, clinical presentation and diagnosis, and treatment will be discussed for each. Other causes of third trimester bleeding will also be identified.
Placenta Previa
In PP, the placenta implants in the lower uterine segment, completely or partially covering the internal cervical os. This condition complicates roughly one in 200 pregnancies in the third trimester, of which 18-20% are classified as complete.1 Of the patients diagnosed with PP in the second trimester, only 5% will have evidence of it late in the third trimester.2 This is because the placenta migrates toward the fundus as the lower uterine segment develops and elongates, effectively alleviating the previa as the pregnancy progresses. Proposed risk factors for development of placenta previa include: multiparity (up to 5% of grand multiparity pregnancies), advanced maternal age, previous cesarian section, history of dilation and curettage, history of myomectomy, large placenta, multiple gestation, and (perhaps) smoking.
The cardinal clinical feature of PP is painless hemorrhage. While spotting may occur earlier in pregnancy, the typical initial hemorrhage occurs after 28 weeks and is sudden and profuse. Thirty percent of patients present before 30 weeks gestation. The peak incidence occurs at 34 weeks. Ten percent will not be diagnosed until labor.2 Attempts to distinguish the vaginal bleeding of PP from that associated with PA focus on the absence of pain in PP and the "fresh" nature of the blood, as opposed to the painful bleeding in abruptio and the dark, "old" appearance of that blood. However, 10-20% of cases of the bleeding of PP may be associated with pain from uterine irritability. This is thought to be due to concurrent marginal PA. Unless there is maternal shock or coexisting PA, the uterus is soft and non-tender, and there is a low incidence of fetal distress.1
The use of ultrasound is indispensable in establishing the diagnosis of PP. Transabdominal ultrasound has a false-positive rate of 2-6%, and a false-negative rate of 7% when used alone.2 The addition of transvaginal ultrasonography has been well-studied in the setting of PP; the accuracy is very high and the safety of the technique is well-established in the controlled setting of the labor and delivery suite.2,3
ED management of the patient with suspected PP should include placement of two large bore intravenous catheters, volume resuscitation for hemodynamic instability, and careful monitoring of the mother and fetus. Lab tests should include a complete blood count, coagulation studies, type and cross-match, and, if concurrent abruption is suspected, fibrinogen and fibrin degradation products. Vaginal exams (including speculum, digital, and endovaginal ultrasound probes) are widely considered to be contraindicated in the ED in patients who are actively bleeding from suspected PP because of the danger of exsanguinating hemorrhage from inadvertent manipulation of the cervix. After hemodynamic stabilization, the patient should be transferred to the appropriate labor and delivery area or facility that has the capability to perform an emergent cesarian section. If the ED has the capability to do continuous fetal monitoring, it should be initiated. Transabdominal ultrasound in the ED is quick, safe, and easy to perform while the patient awaits transfer.
Placental Abruption
PA is the separation (complete or partial) of a normally implanted placenta before birth. The incidence is as high as one in 86 deliveries, but the most severe form, resulting in fetal demise, occurs in one in 750 deliveries. Perinatal mortality varies from 20% to 35%, and major sequelae manifesting as significant neurologic defects in the infant can be as high as 15%. The incidence of PA in the United States is increasing. It accounts for 30% of late pregnancy bleeding.4 Proposed risk factors for PA include: maternal hypertension, short umbilical cord, dietary deficiencies, sudden decompression of amniotic membranes, premature rupture of membranes, severely small-for-gestational-age fetus, maternal age older than 35 years, male fetal gender, cigarette smoking, and maternal cocaine use. Trauma is also a significant cause of PA, complicating 2-4% of minor trauma and up to 40% of major trauma in pregnant women.5
The presentation of patients with PA can be variable, including the amount of vaginal bleeding. External signs of bleeding may be absent in up to 20% of cases. The mother may present in shock, with accompanying fetal distress, and manifest only minimal evidence of external bleeding. The blood is characteristically dark. Significant hemorrhage is frequently concealed or sequestered within the uterus. The hallmark of PA is uterine pain. Findings of uterine tenderness or irritability are usually present with significant PA. The uterus will be firm, contracted, and tender. With significant separations, fetal distress occurs and the maternal coagulation cascade can be triggered, resulting in disseminated intravascular coagulation. Other signs of PA include amniotic fluid leakage and a uterus larger than gestational age.
Unlike PP, a vaginal exam is not likely to make the bleeding of PA worse. Nonetheless, because a significant percentage of patients with PP can have pain as part of their clinical presentation, most caution against performing such an exam unless it is done in the labor and delivery area, which is equipped to perform an emergent cesarian section. The diagnosis of PA is largely clinical, based upon the signs and symptoms described above. The use of ultrasound has not been shown to be significantly helpful in diagnosing abruption, with sensitivities ranging from 2% to 20%.2 Transabdominal ultrasound may be helpful in identifying PP, as well as in establishing fetal well-being and gestational age. However, ultrasound in the ED should not delay resuscitative efforts and transfer of the patient to definitive care.
The management of patients with PA is directed at stabilization of the mother and transfer of the patient from the ED to definitive care. Large bore IVs should be started, and fluid and blood resuscitation initiated to stabilize maternal vital signs. It is imperative to aggressively treat maternal shock, even in the absence of identifiable bleeding. There can be up to two liters of blood sequestered in the uterus in abruption. If continuous fetal monitoring is available in the ED, it should be used. Blood should be sent for routine studies and coagulation studies, as well as type and cross-match, fibrinogen, and fibrin split products. If a coagulopathic state is apparent, treatment with fresh frozen plasma and platelets is indicated. Patients with PA, once stabilized, must be transferred to a labor and delivery area as soon as possible.
Other Conditions Causing Third Trimester Bleeding
There is a variety of other conditions that can cause bleeding late in pregnancy. Because some require a speculum or bimanual exam to diagnose, it is unlikely that they will be diagnosed in the ED. The primary objective in patients with third trimester bleeding is to stabilize the mother and transport her to the appropriate facility. Diagnosis of these less serious entities can then take place in a controlled setting. These conditions include: circumvallate placenta, vasa previa, bloody show associated with labor, cervical polyps, cervical or vaginal ulcers, abrasions or lacerations, maternal blood dyscrasias, and small marginal placental separations that cannot be identified before delivery.
Summary
PP and PA are potentially devastating conditions that can threaten fetal viability and cause maternal morbidity and mortality. The emergency physician must be familiar with the signs and symptoms of these conditions so that prompt recognition can lead to appropriate stabilization of the mother and transfer of the patient to definitive care. Vaginal exams are contraindicated in the ED, and the use of ultrasound, while sometimes providing useful information, should not delay the primary objectives of treatment: resuscitation, monitoring, and transfer.
References
1. Mabie WC. Placenta previa. Clin Perinatol 1992;19: 425-435.
2. Phelan MB, et al. Pelvic ultrasonography. Emerg Med Clin North Am 1997;15:789-824.
3. Farine D, et al. Vaginal ultrasound for diagnosis of placenta previa. Am J Obstet Gynecol 1988;159: 566-569.
4. Saftlas AF, et al. National trends in the incidence of abruptio placentae 1979-1987. Obstet Gynecol 1991;78: 1081-1086.
5. Pearlman MD, et al. Blunt trauma during pregnancy. N Engl J Med 1990;323:1609-1613.
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