This chapter deals primarily with APGO Educational Topic Area:
TOPIC 23 THIRD-TRIMESTER BLEEDING
Students should be able to differentiate the causes and potential complications of third-trimester bleeding and describe the evaluation of a patient with this condition. They should outline a basic approach for initial evaluation and management in a patient with acute blood loss including appropriate use of blood products.
Clinical Case
A visitor to your community, a 26-year-old G1 P0 at 36 weeks of gestational age, presents to your labor and delivery urgent evaluation area. She indicated she has had “some” prenatal care and that everything seemed to be going well until 2 hours earlier when she experienced an episode of vaginal bleeding much like a light menstrual period, except that there was no pain as is usual with her menses. She had no history of bleeding disorders or sexually transmitted diseases and had not been sexually active since about the eighth week of her pregnancy. She had had a pelvic ultrasound at 7 weeks of gestational age because of a concern of ectopic pregnancy, which, obviously, proved unwarranted.
Approximately 4% to 5% of pregnancies are complicated by vaginal bleeding in the third trimester. Bleeding ranges from spotting to life-threatening hemorrhage. Intercourse, trichomonas cervicitis, and recent pelvic examinations are common precipitants of spotting because the cervix is more vascular and friable in pregnancy. Bleeding from hemorrhoids may be mistaken for vaginal bleeding, but the difference is easily distinguished by examination. At term, a woman’s total blood volume increases by about 40% and her cardiac output by about 30%. About 20% of this term cardiac output is shunted to the pregnant uterus, so significant bleeding can be quickly catastrophic. Severe hemorrhage is much less common than spotting but remains a leading cause of maternal and fetal morbidity and mortality. The two most common causes of significant bleeding in the third trimester are placenta previa (in which the placenta is located close to or over the cervical os) and placental abruption (premature separation of the placenta). The paradigm is that painful bleeding usually means placental abruption, whereas painless bleeding usually means placenta previa. Other important causes of bleeding include preterm cervical change, preterm labor, and uterine rupture (see Chapters 15 and 17). In many cases, bleeding remains unexplained or is attributed to local lesions. Possible anatomic causes of third-trimester bleeding are listed in Box 16.1.
HISTORY AND PHYSICAL EXAMINATION
A timely, focused history and physical examination are crucial in assessing third-trimester bleeding once the patient is stable, and a reassuring fetal heart rate pattern is confirmed. Although diagnosis is rarely based solely on history, a differential diagnosis is usually possible after pertinent information has been gathered. It is always important to quantify bleeding and associated symptoms such as abdominal pain. A personal or family history of bleeding with procedures may lead to a diagnosis of a bleeding disorder such as von Willebrand disease, whereas a history of cervical dysplasia and no recent Pap tests would be worrisome for cervical cancer. It is also important to consider bleeding from other organs, such as hemorrhoids from the anus or gross hematuria from acute cystitis.
A physical examination should always begin with maternal vital signs, although significant changes are not seen until the blood loss exceeds 10% to 15% of the total blood volume. The fetal heart rate should be auscultated by either Doppler or electronic fetal monitor or assessed with bedside real-time ultrasound. A general review of respiratory and cardiovascular systems is warranted in all patients. Intravenous (IV) access should be established if the bleeding is heavy, estimated blood loss is significant, or the patient is unstable. A brief inspection for petechiae, or bruising, may be indicated if there is suspicion of a bleeding disorder including a coagulopathy. Abdominal examination should focus on whether the uterus is soft or firm and tender and if signs of hemoperitoneum are present. The presence or absence of bowel sounds can be misleading in this obstetric emergency situation. Bimanual pelvic examination should not be undertaken until placental position is confirmed by ultrasound, inso-far as it could cause hemorrhage by inadvertent detachment of the placenta. Instead, inspection of the vulva may be followed by a careful speculum examination of the vagina and cervix.
BOX 16.1 Causes of Bleeding in the Second Half of Pregnancy
Hemorrhoids
Vulva
Varicose veins
Tears or lacerations
Vagina
Cervix
Polyp
Ectropion
Glandular tissue (normal), which is friable
Severe cervicitis
Carcinoma
Intrauterine
Uterine rupture
Placenta previa
Placental abruption
Placenta accreta, increta, or percreta
Vasa previa
A common finding in pregnancy is a significant ectropion of the cervix, particularly among women with a history of using oral contraceptives. The ectropion is an area on the ectocervix where columnar epithelium has been exposed to vaginal acidity due to eversion of the endocervix. The ectropion may appear reddened and “raw looking,” and mild bleeding can occur. These findings may raise concerns about cancer, but they are actually benign.
Bleeding
Significant bleeding is an obstetric emergency requiring immediate management, including ongoing monitoring of vital signs and sufficient large-bore IV lines for the rapid administration of crystalloid fluid, blood, and blood products. Blood studies should include complete blood count, coagulation profile, and a type and cross match for four units. Regardless of the amount of bleeding, blood type and screen are necessary. Patients who are Rh D-negative may require immunoglobulin to protect against the Rh D antigen, and a Kleihauer-Betke test to determine fetomaternal bleeding should be performed to determine the amount of immunoglobulin needed once the bleeding has been controlled (see Chapter 15). Staff should be ready for delivery, which is facilitated by having a rapid response system in place for such emergency situations. Most likely, this will require an emergency caesarean delivery and, possibly, a general anesthetic. If the bleeding is not sufficient to warrant emergency delivery and/or the fetus is preterm, then blood studies should be continued and IV access maintained. An ultrasound examination should be performed to assess placental location and condition of the fetus. The patient should be admitted to the hospital to allow for close monitoring. Vaginal hemorrhage in the third trimester is one of the few real obstetric emergencies.
PLACENTA PREVIA
Placenta previa is a placental location close to or over the internal cervical os. It can be classified as complete, in which the placenta completely covers the internal os, or partial, in which the placenta overlies part but not all of the internal os. A placenta that extends into the lower uterine segment but does not reach the internal os is called a low-lying placenta (Fig. 16.1).
Painless bleeding in the third trimester is classically associated with placenta previa. In many cases there may be small amounts of bleeding prior to a more significant episode of bleeding. About 75% of women with placenta previa will have at least one episode of bleeding. On average, this episode occurs at around 29 to 30 weeks of gestation. In general, placenta previa occurs in about 1 in 200 pregnancies. The incidence of placenta previa earlier in pregnancy (approximately 24 weeks) is 4% to 5% and decreases with increasing gestational age.
FIGURE 16.1. Placenta previa. (Adapted from Oyelese Y, Smulian JC. Placenta previa, accreta, and vasa previa. Obstet Gynecol. 2006;10(4):927.)
Complete placenta previa rarely resolves spontaneously, but partial and low-lying placenta previa will often resolve by 32 to 35 weeks of gestation. The mechanism does not involve an upward “migration” of the placenta but, rather, a stretching and thinning of the lower uterine segment, which effectively moves the placenta away from the os.
Diagnosis, Etiology, and Risk Factors
Transvaginal ultrasonography is more accurate in diagnosing placenta previa than abdominal ultrasonography, which gives many false-positive results, particularly when the placenta is located posteriorly (Fig. 16.2). The etiology of placenta previa is not known; however, it may be associated with abnormal vascularization. Risk factors for placenta previa include placenta previa in a prior pregnancy (4%–8% recurrence), prior cesarean delivery or other uterine surgery, multiparity, advanced maternal age, cocaine use, and smoking. Placenta previa has been associated with a slight increase in fetal anomalies, although the precise mechanism is unclear. These anomalies include severe cardiovascular, central nervous system, gastrointestinal, and respiratory abnormalities.
Management
The first bleeding episode usually ceases in 1 to 2 hours if it was not severe enough to require delivery. Close observation, frequent blood pressure measurements, fluid administration, bed rest, and administration of steroids for fetal lung maturity may be appropriate if the fetus is premature and the bleeding is not heavy enough to warrant immediate delivery. The bleeding is usually painless, except when it is associated with labor or abruption (the premature separation of the placenta; see Table 16.1 for a comparison of placenta previa and placental abruption). For patients in a stable condition, outpatient management may be considered if the patient is compliant, lives close to the hospital, and has someone with her at all times. If the bleeding is severe or the fetus is at term, then delivery is appropriate.
FIGURE 16.2. Transvaginal sonogram of a complete placenta previa (PP). Note that both the placenta and the internal cervical os (arrow) are clearly depicted. A, anterior lip of cervix; P, posterior lip of cervix. The placenta just overlaps the internal os. (From Oyelese Y, Smulian JC. Placenta previa, accreta, and vasa previa. Obstet Gynecol. 2006;107(4):927.)
Cesarean Delivery
Placenta previa is associated with an increase in preterm birth and perinatal mortality and morbidity. Delivery via caesarean birth is the rule unless it occurs earlier in pregnancy (i.e., at 20 weeks). In a patient whose condition is stable, caesarean delivery can be undertaken at 36 to 37 weeks of gestation, following amniocentesis to confirm fetal lung maturity. If lung maturity is not demonstrated, the patient should be delivered at 37 to 38 weeks of gestation. Earlier caesarean delivery may be required if bleeding occurs or if the patient goes into labor. The number of bleeding episodes is unrelated to the degree of placenta previa or to fetal outcome.
Complications
Complications of placenta previa also include increased bleeding from the lower uterine segment where the placenta was attached at the time of cesarean delivery. The placenta may also be abnormally adherent to the uterine wall. This is termed placenta accreta if the placental tissue extends into the superficial layer of the myometrium, placenta increta if it extends further into the myometrium, or placenta percreta if it extends completely through the myometrium to the serosa, and sometimes into adjacent organs such as the bladder (Fig. 16.3). The incidence of placenta accreta is about 1 in 2,500 deliveries but increases in patients with a history of cesarean delivery. The risk of requiring hysterectomy following a caesarean delivery for patients with placenta previa is increased, which, in turn, increases the risk of maternal and perinatal morbidity and mortality.
FIGURE 16.3. Placenta accreta, increta, and percreta.
PLACENTAL ABRUPTION
Placental abruption refers to an abnormal premature separation of an otherwise normally implanted placenta. There are various types of abruption, depending upon the extent and region of separation. A complete abruptionoccurs when the entire placenta separates. A partial abruption exists when part of the placenta separates from the uterine wall. A marginal abruption occurs when the separation is limited to the edge of the placenta (Fig. 16.4). A significant abruption requiring delivery occurs in 1% of births.
Abruption occurs when bleeding in the decidua basalis causes separation of the placenta and further bleeding. The classic presentation of abruption is vaginal bleeding with abdominal pain. Smaller or marginal abruptions may present with bleeding only. Concealed hemorrhage occurs when blood is trapped behind the placenta and is unable to exit. Painful uterine contractions, significant fetal heart rate abnormalities, and fetal demise may occur in severe cases of concealed placental abruption.
Risk Factors
Risk factors for placental abruption include chronic hypertension, preeclampsia, multiple gestation, advanced maternal age, multiparity, smoking, cocaine use, and chorioamnionitis. Trauma is also a major risk factor, and patients involved in a vehicle accident (even if wearing a seat belt), fall, or other trauma should be evaluated for the possibility of abruption. Typically, fetal heart rate monitoring for a minimum of 4 hours is performed. Abruption in a prior pregnancy increases the risk of abruption in subsequent pregnancies by 15- to 20-fold. An elevated second-trimester maternal serum alpha-fetoprotein (AFP) level may be associated with up to a 10-fold increased risk of placental abruption due to possible entry of AFP into the maternal circulation through the placental uterine interface.
FIGURE 16.4. Types of placental abruption. Note that vaginal bleeding is absent when the hemorrhage is concealed.
Diagnosis and Management
Abruption is often diagnosed by clinical examination, although an ultrasound examination may be useful in less severe cases not requiring immediate delivery. Abruption may occur in the absence of ultrasound findings.
Management of patients with placental abruption includes monitoring of vital signs, fluid administration, and delivery for severe hemorrhage. Expectant management may be appropriate for preterm patients with less severe abruptions and minimal bleeding. Delivery is often by cesarean birth, but vaginal delivery frequently is possible, and may even follow a rapid labor.
Complications
Rarely, blood penetrates the uterus to such an extent that the serosa becomes blue or purple in color. This condition is called Couvelaire uterus. A Kleihauer-Betke or similar test is essential to determine the amount of fetal–maternal hemorrhage. Results guide decisions regarding administration of Rh D immunoglobulin in women who are Rh D-negative and determine the need for blood transfusion in the potentially anemic neonate. Abruption is the most common cause of coagulopathy in pregnancy (see Table 16.1). Platelet counts may be low, and prothrombin time and partial thromboplastin time may be increased. Serum fibrinogen may also be depleted. Disseminated intravascular coagulation is a rare but extremely serious complication.
FIGURE 16.5. Vasa previa. Vessels are seen running unprotected through the membranes. p, placenta. (From Oyelese Y, Smulian JC. Placenta previa, accreta, and vasa previa. Obstet Gynecol. 2006;107 (4):927.)
VASA PREVIA
Vasa previa describes the passage of fetal blood vessels over the internal os below the presenting part of the fetus. It can occur with a velamentous insertion, in which the fetal blood vessels insert into the membranes between the amnion and chorion instead of into the placenta and are not protected by Wharton jelly (Fig. 16.5), or when there is a succenturiate lobe across the os from the main placenta. Vasa previa occurs in 1 in 2,500 pregnancies. Rupture of a fetal vessel occurs rarely in pregnancy, but the risk is greatest with vasa previa. Rupture of a vessel can quickly lead to fetal death, as fetal blood volume is so small. Fetal mortality approaches 60% if rupture is not detected before delivery.
Tests
An Apt test can help distinguish fetal blood from maternal blood and may be useful if the test is rapidly available and bleeding is worrisome but not significant enough to warrant emergency delivery. This test mixes the blood specimen with water to achieve hemolysis. The centrifuged supernatant is mixed with sodium hydroxide (NaOH). Fetal blood remains pink, and maternal blood turns yellow-brown.
Rapidly performed transvaginal ultrasound examination with color Doppler may confirm a vasa previa engendering a rapid delivery—usually caesarean section, although a forceps delivery may be performed if the criteria are met. In actuality, though, complications from vasa previa usually remain unanticipated until unexpected bleeding occurs and is often iatrogenic. When performing artificial rupture of membranes, it is important to ensure that no pulsating vessels are present, which may represent a vasa previa.
UTERINE RUPTURE
Most cases of uterine rupture occur at the site of a prior cesarean delivery. Uterine rupture describes a spontaneous complete transection of the uterus from the endometrium to the serosa. If the peritoneum remains intact, it is referred to as a partial rupture, or uterine dehiscence. With complete rupture and fetal expulsion into the abdomen, fetal mortality ranges from 50% to 75%. Fetal survival depends in large part on whether a substantial portion of the placenta remains attached to the uterine wall until delivery is accomplished. Cesarean delivery is imperative to ensure neonatal survival and decrease maternal morbidity.
Clinical Follow-Up
Her fundal height was consistent with her stated gestational age, and her uterus was not tender to palpation. The Leopold maneuvers are consistent with an unengaged cephalic presentation. There is no history of rupture of membranes. She was immediately placed on an electronic fetal monitor. No uterine contractions were noted, and the fetal heart rate was 140 beats per minute with good variability. Because her signs and symptoms were more consistent with third-trimester bleeding caused by placenta previa rather than placental abruption or other less common causes of third-trimester bleeding, pelvic examination was deferred, and an obstetric ultrasound was obtained. A complete placenta previa was discovered, and an appropriate obstetric management followed.
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