HEMOLYTIC DISEASE OF NEWBORNS
Category: Child Health
Abstract : History: Women at risk for alloimmunization should undergo an indirect Coombs
test and titers at their first prenatal visit. If positive, obtain a paternal
blood type and genotype. Obtain serial maternal titers if the father is
homozygous. If the father is heterozygous, determine fetal blood type by using
polymerase chain reaction testing of fetal cells in amniotic fluid or maternal
circ
History: Women at risk for alloimmunization should undergo an indirect Coombs
test and titers at their first prenatal visit. If positive, obtain a paternal
blood type and genotype. Obtain serial maternal titers if the father is
homozygous. If the father is heterozygous, determine fetal blood type by using
polymerase chain reaction testing of fetal cells in amniotic fluid or maternal
circulation or by performing cordocentesis.
Indicators for severe HDN are
previous children with hemolytic disease, rising maternal antibody titers,
rising amniotic fluid bilirubin concentration, and ultrasonographic evidence of
fetal hydrops (eg, ascites, edema, pleural and pericardial effusions, worsening
biophysical profile, decreasing hemoglobin [Hb]).
The major advance in
predicting the severity of hemolytic disease was the delta-OD 450 reported by
Liley in 1961. The serial values of deviation from baseline at 450 nm and the
wavelength at which bilirubin absorbs light are plotted on a Liley
curve against the gestational weeks. The values above 65% on zone 2 are
indication of direct fetal monitoring by cordocentesis, and hematocrit (Hct)
below 30% or a single value in zone 3 is an indication for intrauterine
transfusion. The modified Liley curve is used to correct for gestation less
than 24 weeks because bilirubin levels normally peak at 23-25 weeks' gestation
for unaffected fetuses.
Physical: The infant born to an alloimmunized
mother shows clinical signs based on severity of the disease. The typical
diagnostic findings are jaundice, pallor, hepatosplenomegaly, and hydrops
fetalis in severe cases. The jaundice typically manifests at birth or in the
first 24 hours after birth with rapidly rising unconjugated bilirubin level.
Occasionally, conjugated hyperbilirubinemia is present because of placental or
hepatic dysfunction in those infants with severe hemolytic disease. Anemia is
most often due to destruction of antibody-coated RBCs by the reticuloendothelial
system, and in some infants, anemia is due to intravascular destruction. The
suppression of erythropoiesis by intravascular transfusion of adult Hb to an
anemic fetus can also cause anemia. Hepatosplenomegaly results from
extramedullary hematopoiesis and leads to portal hypertension, contributing to
ascites. Anemia is not the only cause of hydrops. Excessive hepatic
extramedullary hematopoiesis causes portal and umbilical venous obstruction and
diminished placental perfusion because of edema. Increased placental weight and
edema of chorionic villi interfere with placental transport. Hydrops fetalis
results from fetal hypoxia, anemia, congestive cardiac failure, and
hypoproteinemia secondary to hepatic dysfunction. Commonly, hydrops is not
observed until Hb drops below approximately 4 g/dL (Hct <15%). Clinically
significant jaundice occurs in up to 20% of ABO-incompatible
infants.
Causes: In the absence of a positive direct Coombs test result,
other causes of pathologic jaundice should be considered, including intrauterine
congenital infections; erythrocyte membrane defects; RBC enzyme deficiencies;
and nonhemolytic causes, such as enclosed hemorrhages, hypothyroidism,
gastrointestinal obstruction, and metabolic diseases. Similarly, hydrops can
occur from nonimmune hematologic disorders causing anemia, cardiac failure from
dysrhythmia, congenital heart defects, and infections (eg, syphilis,
cytomegalovirus [CMV], Parvovirus).
• Common causes for HDN
o Rh system
antibodies
o ABO system antibodies
• Uncommon causes - Kell system
antibodies
• Rare causes
o Duffy system antibodies
o MNS and s
system antibodies
• No occurrence in HDN : Lewis system antibodies and P
system antibodies
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