Vaginal Bleeding During Late Pregnancy
Bleeding during late pregnancy (≥ 20 wk gestation, but before birth) occurs in 3 to 4% of pregnancies.
The most common cause of bleeding during late pregnancy is
Bloody show heralds onset of labor, is scant and mixed with mucus, and results from tearing of small veins as the cervix dilates and effaces at the start of labor.
More serious but less common causes (see table Some Causes of Bleeding During Late Pregnancy) include
Abruptio placentae is premature separation of a normally implanted placenta from the uterine wall. The mechanism is unclear, but it is probably a late consequence of chronic uteroplacental vascular insufficiency. Some cases follow trauma (eg, assault, motor vehicle crash). Because some or most of the bleeding may be concealed between the placenta and uterine wall, the amount of external (ie, vaginal) bleeding does not necessarily reflect the extent of blood loss or placental separation. Abruptio placentae is the most common life-threatening cause of bleeding during late pregnancy, accounting for about 30% of cases. It may occur at any time but is most common during the 3rd trimester.
Placenta previa is abnormal implantation of the placenta over or near the internal cervical os. It results from various risk factors. Bleeding may be spontaneous or triggered by digital examination or by onset of labor. Placenta previa accounts for about 20% of bleeding during late pregnancy and is most common during the 3rd trimester.
In vasa previa, the fetal blood vessels connecting the cord and placenta overlie the internal cervical os and are in front of the fetal presenting part. Usually, this abnormal connection occurs when vessels from the cord run through part of the chorionic membrane rather than directly into the placenta (velamentous insertion). The mechanical forces of labor can disrupt these small blood vessels, causing them to rupture. Because of the relatively small fetal blood volume, even a small blood loss due to vasa previa can represent catastrophic hemorrhage for the fetus and cause fetal death.
Uterine rupture may occur during labor—almost always in women who have had scarring of the uterus (eg, due to cesarean delivery, uterine surgery, or uterine infection)—or after severe abdominal trauma.
Some Causes of Bleeding During Late Pregnancy
The evaluation aims to exclude potentially serious causes of bleeding (abruptio placentae, placenta previa, vasa previa, uterine rupture). Bloody show of labor and abruptio placentae are diagnoses of exclusion.
History of present illness should include
Important associated symptoms include abdominal pain and rupture of membranes. Clinicians should note whether these symptoms are present or not and describe them (eg, whether pain is intermittent and crampy, as in labor, or constant and severe, suggesting abruptio placentae or uterine rupture).
Review of systems should elicit any history of syncope or near syncope (suggesting major hemorrhage).
Past medical history should note risk factors for major causes of bleeding (see table Some Risk Factors for Major Causes of Bleeding During Late Pregnancy), particularly previous cesarean delivery. Clinicians should determine whether patients have a history of hypertension, cigarette smoking, in vitro fertilization, or any illicit drug use (particularly cocaine).
Some Risk Factors for Major Causes of Bleeding During Late Pregnancy
Examination starts with review of vital signs, particularly BP, for signs of hypovolemia. Fetal heart rate is assessed, and continuous fetal monitoring is started if possible.
The abdomen is palpated for uterine size, tenderness, and tonicity (normal, increased, or decreased).
A digital cervical examination is contraindicated when bleeding occurs during late pregnancy until ultrasonography confirms normal placental and vessel location (and excludes placenta previa and vasa previa). Careful speculum examination can be done. If ultrasonography is normal, clinicians may proceed with a digital examination to determine cervical dilation and effacement.
If more than a few drops of blood are observed or there are signs of fetal distress, the more serious causes must be ruled out: abruptio placentae, placenta previa, vasa previa, and uterine rupture. However, some patients with abruptio placentae or uterine rupture have minimal visible bleeding despite major intra-abdominal or intrauterine hemorrhage.
Clinical findings help suggest a cause (see table Some Causes of Bleeding During Late Pregnancy):
Light bleeding with mucus suggests bloody show of labor.
Sudden, painless bleeding with bright red blood suggests placenta previa or vasa previa.
Dark red clotted blood suggests abruptio placentae or uterine rupture.
A tense, contracted, tender uterus suggests abruptio placentae.
An atonic or abnormally shaped uterus with abdominal tenderness suggests uterine rupture.
The tests should include the following:
All women with bleeding during late pregnancy require transvaginal ultrasonography, done at the bedside if the patient is unstable. A normal placenta and normal cord and vessel insertion exclude placenta previa and vasa previa. Although ultrasonography sometimes shows abruptio placentae, this test is not sufficiently reliable to distinguish abruptio placentae from uterine rupture. These diagnoses are made clinically, based on risk factors and examination findings (a tense uterus is more common in abruptio placentae; loss of tone is more common in rupture). Rupture is confirmed during laparotomy.
In addition, CBC and type and screen (blood typing and screening for abnormal antibodies) should be done. If bleeding is severe, if moderate to severe abruptio placentae is suspected, or if maternal hypotension is present, several units of blood are cross-matched and tests for disseminated intravascular coagulation (PT/PTT, fibrinogen level, d-dimer level) are done.
The Kleihauer-Betke test can be done to measure the amount of fetal blood in the maternal circulation and determine the need for additional doses of Rh0(D) immune globulin to prevent maternal sensitization.
All patients require IV access for fluid or blood resuscitation, as well as continuous maternal and fetal monitoring.
A digital cervical examination is contraindicated in evaluation of bleeding during late pregnancy until placenta previa and vasa previa are excluded.
In abruptio placentae, vaginal bleeding may be absent if blood is concealed between the placenta and uterine wall.
Uterine rupture is suspected in women with a history of cesarean delivery or other uterine surgery.
Vaginal bleeding may be mild despite maternal hypotension.
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