The differential diagnosis of vaginal bleeding during the second half of pregnancy includes abruptio placentae, placenta previa, preterm labor, and bleeding from various lesions of the cervix and lower genital tract. One-third of fetuses die when vaginal bleeding occurs after 20 weeks of gestation. 13
ABRUPTIO PLACENTAE Abruptio placentae, the premature separation of the normally implanted placenta from the uterine wall, accounts for 30 percent of bleeding in the second half of pregnancy. This complication can occur either spontaneously or as the result of trauma to the abdomen. The spontaneous form is far more common, with hypertension the most common risk factor. Other risk factors include hypertension, increased maternal age, multiparity, smoking, cocaine use, and previous abruptions. Abruption can be complete, partial, or concealed. In concealed abruption, there is little or no vaginal bleeding. However, shock may ensue as the actual blood loss is not evident, and establishing the diagnosis may be delayed. The diagnosis of abruption may be difficult, since clinical signs and symptoms depend on the size of the abruption and the amount of blood loss.
Signs and symptoms include vaginal bleeding (unless concealed), abdominal pain, back pain, uterine tenderness, and uterine irritability. Fetal distress, hypotension, and disseminated intravascular coagulation can develop. Abruptio placentae is frequently misdiagnosed as preterm labor. Complications include fetal death, maternal death from hemorrhage or disseminated intravascular coagulation, fetomaternal transfusion, and amniotic fluid embolism. Laboratory tests that should be ordered include CBC, type and crossmatch, coagulation profile, and renal function studies. Crystalloids should be given to maintain maternal volume status. Emergency obstetrical consultation is necessary whenever abruption is suspected. Cardiotocodynamometry and ultrasound studies are used to monitor fetal well-being, and emergency delivery may be necessary. Some centers may elect to treat small abruptions expectantly. Tocolytics should not be given by the emergency physician in the presence of suspected abruption.
PLACENTA PREVIA Placenta previa, the implantation of the placenta over the cervical os, accounts for 20 percent of bleeding episodes in the second half of pregnancy. Incidence is increased with multiparity and prior cesarean section. The patient presents with painless bright-red bleeding. This complication should be distinguished from the "bloody show," which is passage of a very small amount of bright-red blood mixed with mucus at the onset of labor. Since disruption of the placenta by digital or speculum examination can lead to catastrophic bleeding, digital and speculum examination should be avoided. 14 The safest course is to perform emergency ultrasound studies first.
PREMATURE LABOR AND PREMATURE RUPTURE OF MEMBRANES Preterm (premature) labor is defined as labor prior to 37 weeks' gestation,15 while premature rupture of membranes (PROM) is rupture of membranes prior to onset of labor. Preterm labor, occuring in 10 percent of deliveries, is the leading cause of perinatal death and disease, accounting for approximately 85 percent of neonatal deaths not due to lethal genetic or congenital abnormalities. Three major factors contribute to spontaneous or induced delivery before 34 weeks: (1) PROM, (2) spontaneous preterm labor without PROM, and (3) complications that jeopardize fetal or maternal health, mandating early delivery.
Many known factors are associated with preterm labor. More common ones include: PROM, abruptio placentae, drug abuse (particularly of cocaine and amphetamines), multiple gestations, polyhydramnios, cervical incompetence, and infection. Sexually transmitted diseases, including syphilis, gonorrhea, Chlamydia, and bacterial vaginosis are two to three times more likely to be associated with preterm labor. The presence of low-grade infection is felt to be one of the most important causes of PROM because bacterial colonization can reduce the tensile strength of membranes. 16 Of importance is the association of digital pelvic examinations and increased frequency of PROM. As a result of this finding, cervical examinations should not be performed from 37 weeks gestation unless the results of the examination will clearly influence clinical management. Of course, all digital examinations during pregnancy should be done using sterile gloves.
Labor is defined as regular uterine contractions resulting in progressive cervical effacement and dilatation. When a woman presents to the emergency department with the suspected onset of labor, the date of the last menstrual period should be ascertained and the estimated date of delivery calculated. The gestational age is the number of weeks from the first day of the last menstrual period. If that date is not known, gestational age can be estimated clinically (see Chapter^.). The patient should be asked about the frequency and duration of contractions, about passage of blood-stained mucus ("bloody show"), and whether there has been rupture of membranes, usually signaled by a gush of fluid or constant leakage of fluid.
In addition to the routine physical examination, the fundal height should be measured, fetal heart tones auscultated, and a sterile speculum examination performed. A pooling of fluid in the vaginal vault or leakage of clear fluid from the cervix is evidence of PROM. If there is no fluid, the woman should be asked to press on the fundus or perform a Valsalva maneuver to determine whether there is leakage of fluid. Any fluid should be tested with nitrazine paper (pH > 6.5 indicates amniotic fluid) and swabbed on a glass slide to be examined for ferning, indicating amniotic fluid. The presence of blood or semen may interfere with both of these tests. On visual examination, if the cervix is posterior in the vagina, thick, and closed, it is not yet ripe for labor. If, in contrast, it is midposition to anterior within the vagina, moderately effaced, and approximately 2 cm dilated, the uterus is undergoing changes preparatory to expulsion of the fetus. Tests for Chlamydia, gonorrhea, and group B streptococcus should be performed and secretions examined for bacterial vaginosis. If PROM is suspected or confirmed, digital examination should be deferred if possible or, if performed, should be done using sterile gloves.
A number of critical questions must be considered. Has PROM occurred? Is the woman in premature labor? What is the best estimate of gestational age? Is there fetal distress? Is the woman a candidate for tocolytic therapy? All women suspected of premature labor or PROM require obstetric consultation.
Viability of the fetus is possible at 23 weeks of gestation, but mortality and morbidity rates are extremely high. A number of drugs have been used to inhibit labor, but none is completely effective, and there is potential for serious side effects ( Table 101:6.). Tocolysis was the third most common cause of adult respiratory distress syndrome and death in pregnant women in Jackson, Mississippi, over a 14-year period.17 Since tocolytic drugs can delay delivery by only a few days, the purpose of tocolytic therapy is to allow time for administration of glucocorticoids to speed fetal lung maturity 18 and transport of the mother to a center equipped to provide intensive care for the fetus. If a patient presents to an emergency department in preterm labor and the fetus is not mature enough to do well (prior to 34 weeks' gestation), the patient should be transported to a tertiary care facility that has a high-risk ICU for mother and child. Tocolytic therapy should be started prior to transport rather than attempting to deliver the infant at the initial emergency room.19
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