haemolytic disease of the fetus and newborn

Question 1

mechanism of haemolytic disease of the newborn

Answer 1

Mum –ve
Fatehr +ve
Baby +ve

Mum Anti-D 6mo later

2nd preg – mum generate anti-D - cross placenta – coat fetal red cells- destroy in fetal spleen and liver -> anaemia

Question 2

clinical features of haemolytic disease of the fetus and newborn

Answer 2

maternal IgG Ab cross the placenta
-> destroy fetal RBC
->
* fetal haemolytic anaemia
* hydrops fetalis
* haemolytic disease of the newborn (anaemia + BR - which builds up after birth as not removed by placenta -> kernicterus)

Question 3

prevention of haemolytic disease of the newborn

Answer 3

G&S at booking and 28wks
if Ab present:
* check if dad has ag
* monitor Ab level - if high/rising - more likely to effect fetus
* check ffDNA
* monitor fetus for anaemia - MCA doppler 4wkly intil 28wks then every 2wks
* deliver baby early as HDN worse in last few wks of pregnancy
* if necessary - intrauterine transfusion

Question 4

summarise intrauterine transfusion

Answer 4

Specialised centres, highly skilled

1. needle in umbilical vein
2. At delivery - monitor baby’s Hb and bilirubin for several days as HDN can get worse for few days
3. can treat with phototherapy if mild
4. Can give exchange transfusion severe anaemia
   Note: subsequent pregnancies usually worse – need close monitoring, earlier

Question 5

how do you prevent sensitisation

Answer 5

transfuse anti-D to -ve mums
give at possible sensitisation events eg delivery - within 72hrs
doesnt work if already been sensitised
28wks and 34wks

• baby RBC get coated by anti-D before mum’s reticuloendothelial system can make RhD ab

Question 6

what are the sensitising events

Answer 6

1. Give anti-D at delivery if baby is RhD positive
2. Give anti-D Ig for ‘sensitising events’ during pregnancy, where FMH is likely to occur
   * spontaneous miscarriages if surgical evacuation needed and therapeutic terminations
   * amniocentesis and chorionic villous sampling
   * abdominal trauma
   * external cephalic version
   * stillbirth or intrauterine death

Question 7

what dose of anti-D do you give

Answer 7

250 IU less than 20wks
500IU >20 wks

Kleihauer test if >20wks and at delivery - determine if more anti-D needed if fetal bleed is large

Question 8

other Ab that cause haemolytic disease of the newborn

Answer 8

Anti-c and anti-Kell can cause severe HDN
usually less severe than anti-D
Kell causes reticulocytopenia (stopping erythropoiesis) in fetus as well as haemolysis
IgG Anti-A and anti-B antibodies from Group O mothers can cause mild HDN - usually not severe (phototherapy)

Question 9

what is non-invasive fetal genotyping

Answer 9

prediction of fetal D C c E K status
cfDNA in maternal blood for women that have alloAb
mothers can be prepared for careful monitoring through pregnancy
Also identifies pregnant women who have antigen-negative fetuses and who therefore are not at danger from HDFN

Question 10

use of ffDNA

Answer 10

The ffDNA technique can predict Rh D status of fetus from 11+2 weeks gestation.
At 16 weeks women can be consented for sample for ffDNA testing
Results available in 10 days
If baby Rh D negative – no anti D needed