Neonatal and intrauterine transfusions

Question 1

Red cells for intrauterine or neonatal exchange transfusion

Answer 1

• fresh (<5 days old); if not available consider washed
• irradiated
• group O
• negative for maternal antibody that is active
• preferably serologically tested CMV negative or CMV risk reduced (leukoreduced) in intrauterine transfusion or neonate <1200 g who are CMV negative
• 15 ml/kg

Question 2

Plasma or plasma containing products for neonates/intrauterine

Answer 2

• must be compatible with neonates RBCs
• FFP given at 10 ml/kg
• platelets given at 5 ml/kg
• cryoprecipitate given at 10-20 ml/kg

Question 3

maternal immune thrombocytopenic purpura

Answer 3

• risk of neonatal thrombocytopenia
  
  • caused by autoantibodies that cross the placenta
  • may be complicated by severe neonatal thrombocytopenia (<50,000) and serious hemorrhage
• management
  
  • supportive platelet transfusions are sparingly given, typically with active bleeding
  • monitor serial platelet counts for a few days after delivery

Question 4

Cause of NAIT

Recurrence rate of NAIT

Answer 4

• Most commonly caused by maternal alloantibodies directed against HPA-1a
  
  • 2% of individuals are HPA-1a negative
  • can develop anti HPA-1a antibodies if exposed through transfusion or pregnancy
• likelihood of recurrence in subsequent pregnancy is high
• NAIT can affect the first pregnancy
• more severe with each successive pregnancy

Question 5

Management of NAIT

Answer 5

• 20% incidence of intracranial hemorrhage overall; about half of hemorrhages occur in utero
• treatment should begin as soon as the diagnosis is suspected
• high dose IVIg and/or corticosteroids
• Intrauterine platelet transfusion may begin at 18-20 weeks gestation, with antigen negative platelets
• maternal platelets may be used if they have been washed and irradiated
• delivery by C section is recommended
• After birth the risk of hemorrhage is greatest during the first 24-36 hours of life, so expedient platelet transfusion is a good idea

Question 6

HDFN

Answer 6

• Results from maternal alloantibodies crossing placenta
• can lead to appearance of bilirubin in the amniotic fluid, progressive fetal anemia and eventual hydrops fetalis
• to be significant the maternal alloantibody must be IgG1, IgG3, or IgG4

Question 7

Rh HDFN causes

Answer 7

caused by maternal anti D antibodies

• mom must have prior exposure to D+ RBCs; sources:
  
  • prior pregnancy
  • chorionic villus sampling
  • amniocentesis
  • cordocentesis
  • abortion, threatened or complicated
  • placental abruption
  • trauma

Question 8

Prevention of Rh HDFN

Answer 8

• Check pregnant woman’s D status and check D- women for antibodies
• D negative women without antibodies: prophylactic globulin RhIg) given at intervals and whenever a fetal maternal hemorrhage occurs
• D negative women with anti D antibodies: determine titer
  
  • if titer < 16 then severe hemolysis is unlikely
  • if titer is at least 16, monitor degree of fetal hemolysis with either
    
    • amniotic fluid sampling with plotting of OD450 on Liley curve
    • noninvasive Doppler US measurements of MCA flow

Question 9

Tests for fetomaternal hemorrhage

Answer 9

• Rosette test (qualitative)
  
  • maternal blood is incubated with anti D antibody and D+ indicator cells, which form rosettes around D+ fetal cells
  • will detect 10 ml of fetal blood
  • if this test is negative and FMH is still suspected then 300 ug dose of RhIg is given
  • if positive then a quantitative test (KB, ELAT, or flow) is done
• Kleihauer-Betke (acid elution)
  
  • HbF is resistant to acid elution
  • maternal blood is subjected to acid elution then eosin stained; any cells that take up stain (rather than appearing as ghosts) represent cells containg HbF
  • a cell count is performed to determine the percentage of fetal red cells

Question 10

Treatment for D negative woman bearing D+ or D unknown baby

Answer 10

• Prophylactic 300 ug (1 full dose vial) at 28 weeks and again at term
• without RhIg the risk of developing anti D is 16%; with RhIg as above the risk is 0.1%
• FMH
  
  • in first 12 weeks give minidose (50 ug) or a full dose (300 ug)
  • After 12 weeks, a full dose is given
  • additional doses given as needed

Question 11

Calculating the dose of RhIg

Answer 11

• assume maternal blood volume is 5000 ml (otherwise volume = weight x 70 ml/kg)
• determine proportion of fetal cells by KB or other test (count 2000 cells)
• Dose (vials) = maternal blood volume (ml) x proportion of fetal cells in maternal blood / 30
• divide by 30 because each vial protects against 30 ml of whole blood or 15 ml of RBCs
• always add 1 vial to dosage (e.g., 3.3 needs 4 vials and 3.6 needs 5 vials)
• no more than 5 vials should be given IM at one time; larger doses may be divided or given IV

Question 12

Non-Rh HDFN

Answer 12

• due to ABO is most common type
  
  • clinically mild
  • seen in blood group O moms with A or B fetus
  • mediated by IgG and anti A, B antibody
  • may affect first pregnancy
• HDFN due to Kell is most common cause of severe HDFN
  
  • K is expressed early in RBC maturation thus there is destruction of marrow precursors as well as circulating RBCs
  • a maternal critical titer for anti Kell antibody is 8
• Anti C is second most common cause of severe HDFN

Question 13

Lab testing for HDFN

Answer 13

• type and screen on maternal blood
• cord blood from newborn subjected to ABO/Rh typing and DAT, including Rh testing for weak D since weak D fetal RBCs can sensitize D negative moms
• If cord blood DAT is positive
  
  • and maternal antibody screen is positive, then identity of maternal antibody is determined by red cell panel
  • if maternal antibody screen is negative, then there are multiple possibilities:
    
    • ABO HDFN
    • prior to RhIg administration
    • fetal low incidence antigens that are not present on the screen cells (may need extended panel)
  • next check neonatal bilirubin serially