MLT GlobeBlood Banking: HDFN
56 Blood Banking MCQs on HDFN with answers and explanations.
Which maternal antibodies are unable to cross the placenta and therefore do not cause haemolytic disease of the fetus?
Only IgG is transported across the placenta by the neonatal Fc receptor. Pentameric IgM, like most anti-A and anti-B, stays in the maternal circulation.
A RhD-negative, unsensitised pregnant woman carries a RhD-positive fetus. What is given to prevent anti-D formation?
Anti-D at about 28 weeks and within 72 h of delivery clears fetal D-positive cells before the mother's immune system responds.
A woman with anti-D has a partner who is D-positive and heterozygous for RHD. What is the chance that each fetus is D-positive?
A heterozygous (D/d) father passes the RHD gene to half of his children. A homozygous father would give a D-positive fetus in every pregnancy.
Which tests are routinely performed on cord blood of an infant born to a mother with a clinically significant antibody?
Cord blood ABO, D type and DAT show whether the infant has antigen-positive cells coated with maternal antibody. Reverse grouping is not useful in newborns.
Why is ABO typing of a newborn usually limited to forward (cell) grouping?
Infants do not form their own ABO antibodies until about 3–6 months; any present came from the mother. Reverse grouping would give misleading results.
What are the main goals of exchange transfusion in a newborn with severe HDFN?
Exchange removes unconjugated bilirubin, sensitized red cells and free maternal antibody, while giving antigen-negative red cells to correct anemia.
Phototherapy lowers bilirubin in newborns with HDFN by:
Blue light changes unconjugated bilirubin into photoisomers that are excreted in bile and urine without conjugation. It does not affect maternal antibody.
A D-negative woman without anti-D delivers a baby whose cord cells type D-negative, including a weak D test. What should be done?
RhIG prevents immunization by D-positive fetal cells. If the infant is D-negative, there is no D exposure, so RhIG is not indicated.
One 300 µg dose of RhIG protects against a fetal bleed of about:
A standard 300 µg dose covers about 30 mL of fetal whole blood, which is about 15 mL of fetal red cells.
After delivery of a D-positive baby, RhIG should be given to an eligible D-negative mother within:
Postpartum RhIG should be given within 72 hours of delivery. If missed, it may still be given up to 28 days, but it is less effective.
Why do Lewis antibodies not cause HDFN?
Lewis antibodies are usually IgM, which cannot cross the placenta, and fetal and newborn red cells express little Lewis antigen.
At the first prenatal visit, which blood bank tests are routinely performed on every pregnant woman?
All pregnant women should have ABO, D and an antibody screen early in pregnancy to detect clinically significant antibodies and identify RhIG candidates.
Hemolytic disease of the fetus and newborn is caused by:
In HDFN, maternal IgG against a fetal red cell antigen (such as D) crosses the placenta and coats fetal red cells, which are then destroyed.
Kernicterus in a newborn with HDFN is caused by:
Very high unconjugated bilirubin is fat-soluble and can cross into the brain, causing permanent damage. Phototherapy and exchange transfusion aim to prevent it.
A D-negative pregnant woman without anti-D has an amniocentesis. What should she receive?
Amniocentesis can cause fetomaternal bleeding, so a non-sensitized D-negative woman should receive RhIG.
HDFN was historically called 'erythroblastosis fetalis' because:
The anemic fetus releases large numbers of erythroblasts (nucleated red cells) into its circulation.
The most frequent form of HDFN is:
ABO HDFN, mainly in group A or B babies of group O mothers, is the most common form but is usually mild.
Most infants who need treatment for ABO HDFN are managed with:
ABO HDFN is usually mild, and phototherapy is enough in most cases. Exchange or intrauterine transfusion is rarely needed.
After an RhD-negative mother delivers an RhD-positive baby, which test estimates fetomaternal hemorrhage to calculate the anti-D dose?
Fetal cells containing HbF resist acid elution and stain pink, allowing counting of fetal cells in maternal blood; flow cytometry is an alternative. The Singer test measures HbF, not cells.
Which statement about ABO hemolytic disease of the newborn is correct?
Group O mothers often have IgG anti-A,B that crosses the placenta, so the first baby can be affected. Disease is usually mild because fetal A and B antigens are weak, and the DAT is often weak or negative.