HDFN

Flashcards about hemolytic disease of the fetus and newborn, its diagnosis, and management.

What is HDFN?

Hemolytic Disease of the Fetus and Newborn; destruction of fetal/neonate RBCs by maternal antibodies.

What immunoglobulin class is actively transported across the placenta?

IgG

What did Levine and Stetson report in 1939?

A transfusion reaction from transfusing a husband's blood to a postpartum woman, postulating immunization to the father's antigen via fetomaternal hemorrhage (FMH).

What is the nature of Rh antibodies?

Immune antibodies

What blood type is nearly always limited to ABO HDFN?

A and B infants of group O mothers

Can ABO HDFN occur in the first pregnancy?

Yes

What are characteristics of ABO HDFN?

Microspherocytes and increased RBC fragility

What are the serious consequences seen with other causes of HDFN that are extremely rare in ABO-induced HDFN?

Stillbirth, hydrops fetalis, and kernicterus.

In Rh(D) HDFN, why is the Rh-positive firstborn infant of an Rh-negative mother usually unaffected?

The mother has not yet been immunized.

How does maternal anti-D affect subsequent offspring?

It crosses the placenta and binds to fetal Rh-positive cells, affecting subsequent D antigen inheriting offspring.

What percentage of women experience transplacental hemorrhage of fetal RBCs into maternal circulation during gestation?

Up to 7%

What interventions can increase the risk of fetomaternal hemorrhage?

Amniocentesis, chorionic villus sampling, and trauma to the abdomen.

Which IgG subclasses are more efficient in RBC hemolysis?

IgG1 and IgG3

Besides Anti-D, which non-Rh system antibody is considered the most clinically significant in the ability to cause HDFN?

Anti-Kell

How does ABO incompatibility protect against Rh immunization?

By the hemolysis in the mother's circulation of ABO incompatible D-positive fetal RBCs before D antigen recognition.

What is erythroblastosis fetalis?

The release of immature fetal RBCs (erythroblasts) into the circulation due to fetal RBC destruction and resulting anemia.

What causes hydrops fetalis?

Severe anemia and hypoproteinemia leading to high-output cardiac failure with generalized edema, effusions, and ascites.

What maternal organ metabolizes unconjugated bilirubin?

Liver

What can unconjugated bilirubin levels greater than 18 to 20 mg/dL cause in newborns?

Kernicterus

What is the recommended obstetric practice at the first prenatal visit?

To perform type and antibody screen, preferably in the first trimester

At which temperature must methodology detect clinically significant IgG antibodies?

37°C and in the antiglobulin phase

What can a complete Rh phenotype determine if the mother has anti-D and the father is D-positive?

The chance of being homozygous or heterozygous for the D antigen

What is the significance of an antibody titer repeatedly at 32 or above?

Indication for Color Doppler Middle Cerebral Artery Peak Systolic Velocity studies after 16 weeks gestation to determine fetal anemia.

What finding using MCA-PSV indicates significant fetal anemia?

Findings of >1.5 multiples of mean (MoM).

What conditions necessitate intrauterine transfusion?

MCA-PSV indicates momia (>1.5 MoM), Fetal hydrops on ultrasound, Cordocentesis blood sample has a fetal hemoglobin level of less than 10 g/dL

What is the goal of intrauterine transfusion?

To maintain fetal hemoglobin above 10g/dL

What wavelength is used in phototherapy to treat hyperbilirubinemia?

460 to 490 nm

How does IVIG treat hyperbilirubinemia of the newborn caused by HDFN?

IVIG competes with the mother's antibodies for the Fc receptors on macrophages in the infant's spleen, reducing hemolysis.

What are the advantages of exchange transfusion?

Removal of high levels of unconjugated bilirubin, circulating maternal antibody, sensitized RBCs, and replacement of incompatible RBCs with compatible RBCs.

What blood group is preferred for intrauterine and neonatal transfusions in HDFN cases?

Group O RBCs

What characteristics should blood for intrauterine and neonatal transfusions have?

Antigen-negative for maternal antibodies, leukocyte-reduced, irradiated, Hemoglobin S negative, and CMV-negative.

What is the mechanism of action of RhIG?

Interferes with B-cell priming to make anti-D, although other modes of action may occur

When is the first dose of RhIG typically provided?

At 28 weeks of gestation

When should RhIG be administered after delivery?

Within 72 hours

What can IV injections of intramuscular preparations of RhIG cause?

Severe anaphylactic reactions

What test is used to determine the volume of fetal hemorrhage?

Kleihauer-Betke test or flow cytometry

How does the Kleihauer-Betke test work?

Maternal blood smear is treated with acid, fetal cells (containing Hgb F) remain pink, and maternal cells appear as ghosts.

RhIG is of no benefit once a person __.

has been actively immunized and has formed anti-D.