In abruptio placentae, also called placental abruption, the placenta separates from the uterine wall prematurely, usually after the 20th week of gestation, producing hemorrhage. Abruptio placentae occurs most often in multigravidas - usually in women over age 35-and is a common cause of bleeding during the second half of pregnancy. Fetal prognosis depends on gestational age and amount of blood lost; maternal prognosis is good if hemorrhage can be controlled.
Causes of abruptio placentae
The cause of abruptio placentae is unknown. Predisposing factors include trauma (such as a direct blow to the uterus resulting from abuse or accidental trauma), placental site bleeding from a needle puncture during amniocentesis, chronic or pregnancy-induced hypertension (which raises pressure on the maternal side of the placenta), multiparity more than 5, short umbilical cord, dietary deficiency, smoking, advanced maternal age, and pressure on the vena cava from an enlarged uterus.
In abruptio placentae, blood vessels at the placental bed rupture spontaneously owing to a lack of resiliency or to abnormal changes in uterine vasculature. Hypertension complicates the situation, as does an enlarged uterus, which can't contract sufficiently to seal off the tom vessels. Consequently, bleeding continues unchecked, possibly shearing off the 'placenta partially or completely. Typically, such bleeding is external or marginal (in about 80% of patients) if a peripheral portion of the placenta separates from the uterine wall; it's internal or concealed (in about 20% of patients) if the central portion of the placenta becomes detached and the stillintact peripheral portions trap the blood. As blood enters the muscle fibers, complete relaxation of the uterus becomes impossible, increasing uterine tone and irritability. If bleeding into the muscle fibers is profuse, the uterus turns blue or purple and the accumulated blood prevents its normal contractions after delivery (Couvelaire uterus, or uteroplacental apoplexy).
Signs and symptoms of abruptio placentae
Abruptio placentae produces a wide range of clinical effects, depending on the extent of placental separation and the amount of blood lost from maternal circulation. Mild abruptio placentae (marginal separation) develops gradually and produces mild to moderate bleeding, vague lower abdominal discomfort, mild to moderate abdominal tenderness, and uterine irritability. Fetal heart tones remain strong and regular.
Moderate abruptio placentae (about 50% placental separation) may develop gradually or abruptly and produces continuous abdominal pain, moderate dark red vaginal bleeding, a tender uterus that remains firm between contractions, barely audible or irregular and bradycardic fetal heart tones and, possibly, signs of shock. Labor usually starts within 2 hours and often proceeds rapidly.
Severe abruptio placentae (70% placental separation) develops abruptly and causes agonizing, unremitting uterine pain (described as tearing or stabbing); a boardlike, tender uterus; moderate vaginal bleeding; rapidly progressive shock; and absence of fetal heart tones.
In addition to hemorrhage and shock, complications of abruptio placentae may include renal failure, disseminated intravascular coagulation (DIe), and maternal and fetal death.
Diagnostic measures for abruptio placentae include observations of clinical features, pelvic examination (under double setup), and ultrasonography to rule out placenta previa.CLINICAL TIP Draw a line at the level of the fundus and check it every 30 minutes. If the level of the fundus increases, suspect abruptio placentae.
Decreased hemoglobin (Hb) levels and platelet counts support the diagnosis. Periodic assays for fibrin split products aid in monitoring the progression of abruptio placentae and detecting the development of DlC.
Treatment of abruptio placentae is designed to assess, control, and restore the amount of blood lost; to deliver a viable infant; and to prevent coagulation disorders. Immediate measures for abruptio placentae include starting LV. infusion (via a large-bore catheter) of appropriate fluids (lactated Ringer's solution) to combat hypovolemia; placing a central venous line and urinary catheter to monitor fluid status; drawing a blood sample for Hb level and hematocrit determination, coagulation studies, and typing and crossmatching; initiating external electronic fetal monitoring; and monitoring maternal vital signs and vaginal bleeding.
After determination of the severity of abruption and appropriate fluid and blood replacement, prompt delivery by cesarean section is necessary if the fetus is in distress. If the fetus isn't in distress, monitoring continues; delivery is usually performed at the first sign offetal distress. Because of possible fetal blood loss through the placenta, a pediatric team should be ready at delivery to assess and treat the newborn for shock, blood loss, and hypoxia. If placental separation is severe and there are no signs of fetal life, vaginal delivery may be performed unless uncontrolled hemorrhage or other complications contraindicate it.
Complications of abruptio placentae require appropriate treatment. For example, DlC requires immediate intervention with heparin, platelets, and whole blood to prevent exsanguination.
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