Hemolytic Disease of Fetus and Newborn Flashcards
Direct Antiglobulin (Coombs) Test
- Test used to detect for autoimmune hemolytic anemia due to immune system breaking down RBCs
Indirect Antiglobulin (Coombs) Test
- Test given to pregnant women to determine if Rh sensitization has occurred and if the fetus is at risk or not
Erythroblastosis (Hydrops) fetalis pathogenesis
- In the first pregnancy usually during the time of delivery (can alos occur during pregnancy) there is a mixing of a Rh+ fetus blood with an Rh- mother
- Sensitization to Rh factor occurs for the mother, immune memory cells (Plasma cells IgG) for Rh are created and in the 2nd pregnancy if there is mixing w/ another Rh+ fetus, the memory cells or immunoglobulins can go across the placenta and attack the fetal blood and can result in fetal anemia and in extrem cases heart failur and death
Erythroblastosis (Hydrops) fetalis presentation
- Profound hemolysis
- Hyperbilirubinemia
- Fetal anemia
- High output heart failure
- Pallor
- Hepatosplenomegaly
- Massive edema (ascites; pleural and pericardial effusions; placentalomegaly; skin edema)
Rhogam
- Medication given to pregnant women to prevent their immune system from recognizing Rh factor and mounting an immune response
- Unknown mechanism of action
- Given only to Rh- mothers who are not sensitized
Etiologies of Rh sensitization
- Delivery (vaginal/cesarean)
- Prenatal diagnosis (CVS; Amniocentesis)
- Blunt trauma to the gravid abdomen
- Antenatal hemorrhage (Placenta previa; abruption)
- External cephalic version
- Ectopic pregnancy
- Spontaneous abortion
- Elective abortion
- Hydatidiform mole
- Vaginal bleeding
How is a mother diagnosed as being Rh negative?
- A mother who has not undergone Rh sensitization will have an absence of anti-(D) antibodies)
Anti-Rh(D) Immune Globulin Administration Process
- Check ABO blood type and Indirect Coombs (IAT) antibody screen at first obstetrical visit
- If Rh neg. rule out Rh sensitization (absence of anti-(D) antibodies)
- At 28wks, repeat Indirect Coombs (IAT) antibody screen to rule out Rh sensitization
- If no evidence of Rh sensitization, then administer 300mcg anti-Rh(D) Immune Globulin (IM or IV) at 28 weeks gestation
- Following delivery, if newborn is Rh+, then administer 300mcg of anti-Rh(D) Immune Globulin
Treatment of Rh sensitizing event in mother
Sensitizing event being trauma to abdomen, fetal-maternal hemorrhage
- Routinely administer anti-Rh(D) immune globulin within 72hrs of event
- Some benefit noted upon administration within 28 days of event
- Do not adminster if Rh sensitization occurs
300mcg Anti-Rh(D) Immune Globulin prevents Rh sensitization for up to how much fetal blood?
- 30 cc’s (a lot of fetal blood)
Rosette Test
- Test used to determine if more RHIG is necessitated from a fetal-maternal hemorrhage
*Negative test = 300mcg RHIG (means theres been no fetal-maternal blood mixing and so we are trying to further prevent the chance of sensitization)
*Positive test = perform Kleihauer-Betke Stain
Rh Sensitization Management
If the indirect Coombs is pos. for Rh(D) antibodies:
- Evaluate the antibody titer every 4wks until 24wks gestation, and then every 2wks therafter, until it reaches a critical threshold
- The critical threshold is that Rh(D) Ab titer at which level the risk for fetal hemolysis is significant
- The critical threshold varies w/ each hospital lab, but is usually considered to be 1:16 or 1:32
- Rh(D) titers are expressed as follows: 1:1, 1:2, 1:4, 1:8, 1:16, 1:32, 1:64, 1:128, 1:256, etc…
Management once the critical Rh(D) Ab level is reached
Evaluate paternal Rh(D) zygosity:
- If paternal zygosity is heterozygous, then perform amniocentesis to evaluate fetal Rh(D)
- If fetus is Rh(D)+, or if father is Rh(D) homozygous, then the fetus is at risk for HDFN:
- Perform serial evaluations (every 1-2wks) for fetal anemia, by either:
*1-serial amniocenteses for OD450 on spectrophotometric curve or…
*2-doppler evaluation of the fetal middle cerebral artery peak systolic velocity
