Questions and Answers
What is the most common cause of fetal anemia?
Which condition is a direct result of alloimmunization during pregnancy?
Progressive fetal anemia can lead to which of the following complications?
What infectious agent is commonly associated with fetal anemia?
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Which of the following conditions is NOT a cause of fetal anemia?
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What is the principle behind red cell alloimmunization?
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What is primarily used to detect alloimmunization?
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Which procedure can be a cause of fetomaternal hemorrhage associated with red cell antigen alloimmunization?
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Which of these is NOT a potential cause of fetal loss associated with alloimmunization?
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IgG antibodies are primarily associated with which aspect of red cell alloimmunization?
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What is a potential fetal effect of significant acute fetomaternal hemorrhage?
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Which laboratory test is used to quantify fetal red cells in the maternal circulation?
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What treatment is recommended for a fetus with critical anemia due to fetomaternal hemorrhage?
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When is fetal blood sampling and intrauterine transfusion typically performed?
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What maternal condition is an indicator of fetomaternal hemorrhage during evaluation?
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What is hydrops fetalis characterized by?
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How can hydrops fetalis be diagnosed prenatally?
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What is clinically significant edema defined as in sonography?
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What is an abnormal finding in placentomegaly during the second trimester?
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What does the diagnosis of hydrops fetalis particularly include when examined sonographically?
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What is the primary type of hydrops that accounts for at least 90 percent of cases?
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Which genetic condition is the most frequently observed aneuploidy associated with nonimmune hydrops?
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What is the most common infectious agent associated with nonimmune hydrops?
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What approximate percentage of nonimmune hydrops cases is attributed to cardiovascular abnormalities?
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What is the neonatal survival rate for infants diagnosed with hydrops?
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Study Notes
Fetal Anemia Overview
- Fetal anemia is a condition where the fetus has a lower than normal number of red blood cells.
- Most commonly caused by red cell alloimmunization, where maternal antibodies cross the placenta and destroy fetal red blood cells.
Alloimmunization and Its Effects
- Red cell alloimmunization can lead to erythroblastosis fetalis, characterized by the overproduction of immature red blood cells in the fetus and newborn.
- This process can result in hemolytic disease of the fetus and newborn (HDFN), affecting fetal health significantly.
Other Causes of Fetal Anemia
- Infectious agents, particularly Parvovirus B19, can contribute to fetal anemia.
- Hematologic conditions such as alpha-thalassemia and erythroblastosis fetalis also play a role.
- Fetomaternal hemorrhage refers to the transfer of fetal blood cells into maternal circulation, contributing to anemia.
Consequences of Progressive Fetal Anemia
- Progressive anemia from any cause can lead to serious complications, including:
- Heart failure in the fetus.
- Hydrops fetalis, a condition characterized by abnormal fluid accumulation in the fetus.
- Potentially fatal outcomes if not appropriately managed or treated.
Red Cell Alloimmunization
- Principle: Individuals lacking a specific red cell antigen may produce antibodies upon exposure to that antigen.
- Typical scenario: A fetus inherits a red cell antigen from the father, which the mother does not possess.
- Sensitization occurs when sufficient fetal erythrocytes enter the mother's circulation, triggering an immune response.
Detection of Alloimmunization
- Methods: Blood typing and antibody screening are essential for detection.
- Antibody types: The focus is on IgG antibodies rather than IgM due to their role in immune responses.
Causes of Fetomaternal Hemorrhage Related to Alloimmunization
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Pregnancy complications:
- Ectopic pregnancy can lead to alloimmunization.
- Spontaneous abortion may result in fetal blood exposure.
- Elective abortion procedures potentially expose the mother to fetal antigens.
- Fetal death at any trimester can result in maternal sensitization.
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Medical procedures:
- Chorionic villus sampling may cause fetal blood to enter maternal circulation.
- Amniocentesis risk includes introduction of fetal red blood cells into the mother’s system.
- Fetal blood sampling can notably contribute to alloimmunization.
- Evacuation of a molar pregnancy risks maternal sensitization.
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Other risk factors:
- Delivery processes might lead to intermixing of blood between fetus and mother.
- Abdominal trauma could cause fetal hemorrhage into maternal circulation.
- Placental abruption is a significant cause, allowing fetal cells to enter the mother’s bloodstream.
- Unexplained vaginal bleeding during pregnancy raises concern for possible fetal blood exposure.
- Manual removal of the placenta might lead to mixing of blood types.
- External cephalic version may also contribute to fetomaternal hemorrhage.
Fetomaternal Hemorrhage Overview
- Significant acute hemorrhage is poorly tolerated by the fetus, leading to severe complications.
- Fetal neurological impairment can arise from cerebral hypoperfusion, ischemia, and infarction due to fetomaternal hemorrhage.
- Identification of fetomaternal hemorrhage typically occurs during stillbirth evaluations.
Laboratory Testing
- The acid elution or Kleihauer-Betke (KB) test quantitatively detects fetal red blood cells in maternal circulation.
- Measurement of Hemoglobin F provides critical information regarding fetal blood presence.
- Evaluation includes quantification of hemorrhage volume for appropriate clinical response.
Treatment Protocols
- Fetal blood transfusion is a key treatment for fetomaternal hemorrhage.
- Fetal blood sampling and intrauterine transfusion are commonly performed before 34 to 35 weeks of gestation.
- Transfusion interventions are recommended when fetal hematocrit levels indicate a need for medical intervention.
Definition of Hydrops Fetalis
- Excessive accumulation of serous fluid in the fetal compartments, resulting in fetal edema.
- Condition may lead to stillbirth if not detected and managed appropriately.
Diagnosis
- Typically diagnosed after delivery of edematous neonates, often stillborn.
- Growing prevalence of prenatal diagnosis through sonography.
Sonography/Ultrasound Criteria
- Defined as presence of two or more fetal effusions: pleural effusion, pericardial effusion, ascites, or one effusion combined with anasarca (generalized edema).
- Clinically significant edema identified sonographically if skin thickness exceeds 5 mm.
- Placentomegaly observed if placenta thickness is 4 cm or more in the second trimester or 6 cm or more in the third trimester.
Immune Hydrops
- Pathophysiology remains unclear.
- Alloimmunization is a crucial factor in the condition.
- The incidence of immune hydrops has decreased due to the use of Anti-D Immunoglobulin Therapy.
Nonimmune Hydrops
- Accounts for at least 90% of hydrops cases.
- Etiology varies based on the timing of detection during gestation.
- Prenatal identification is linked to various causes:
- Aneuploidy: approximately 20% of cases.
- Cardiovascular abnormalities: around 15%.
- Infections: about 14%, with parvovirus B19 being the most prevalent.
- The neonatal survival rate for affected infants is approximately 50%.
- The most common aneuploidy associated with nonimmune hydrops is Turner syndrome (45,X).
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Description
This quiz explores the causes and effects of fetal anemia, with a particular focus on red cell alloimmunization and its consequences, such as erythroblastosis fetalis. It discusses various infectious and hematologic conditions that can lead to hemolytic disease of the fetus and newborn (HDFN). Test your knowledge on this critical topic in prenatal health.
