HDN Flashcards
Cause of HDN
Development of anti_D in D negative woman following exposure to D positive red cells. Antibody crosses placenta and coats D positive cells
Other significant antibodies
D, c, K
Hydrops
Primarily hepatic in origin: hepatosplenomegaly, portal HTN, hypoalbuminaemia, anasarca
Kernicterus
Deposition of bilirubin in basal ganglia
- neurosensory deafness
- spastic chroathetosis
- mental retardation
Incidence of alloimmunisation
10.2 per 10000 live births
Less than 10% requiring transfusion
IUT due to antibodies
85% anti D
10% anti- Kell
3.5% anti-c
Causes of Feto-maternal haemorrhage
Delivery (including c/s) Abortion APH ECV Closed abdominal injury Ectopic pregnancy IUFD SB Amino CVS FBS Embryo reduction
If antibody screen positive at booking then need to do the following:
Antibody identification Antibody quantitative Testing protocol Paternal screening Fetal genotype gets Post-delivery ABO/D group/Hb/DAT/bilirubin
Testing protocol (frequency of testing)
Anti-D, c, K : 4 weekly to o28/40 then 2 weekly to gestation
Others: booking and 28 weeks
Assessing severity of HDFN
Antibody titres (1:32)
Quantitative of antibodies - if Anti D more than 15- high risk hydrops
MCA PSV
Fetal USS
Invasive monitoring with umbilical blood sampling
Fetal blood typing
Indicators of high fetal risk of HDN —>refer to FMU
Hx of non-ABO HDFN requiring transfusion, irrespective of antibody
Anti-D >10iu/ml
Anti-K: untransfused women, partner K+
Rising anti-c (>20IU)
Role of MCA and PSV
Reciprocal relationship between fetal Hb & velocity of cerebral flow
In fetal anaemia - blood velocity is increased
Must do at a 0 degree angle
Useful between 16-35 weeks
If >1.5MoM then prediction of anaemia 100% with 12% false positive
Other USS signs of fetal anaemia
Placental thickness, UV diameter, liver length, spleen perimeter: useful to assess fetal maturity, does not identify early fetal disease —>changes visible only once hydrops has occurred, weak correlation with fetal hcg/HB
Doppler- detects early fetal anamia
DAT - direct antiglobulin test must be done in any IAT reactive antibody present in pregnancy — results
If DAT +ve: heck Hb and Bili to dx HDN
If DAT negative, no risk of HDN
Management of alloimmunisation during pregnancy
Intrauterine red cell transfusions
IVigG
Premature delivery
How IUT works
IUT supresses erythropoietin causing hypoproliferative anaemia in the neonatal period- may need top ups
Can expect normal developmental outcomes
When to deliver
After 35/40 if severe
If titre stays less than critical and first pregnancy - 39 weeks
If critical to tire or if IUTs- 37 - 38 weeks
Management of neonate
Samples after delivery
Exchange transfusions
Phototherapy
Top-up transfusions
When to give Anti-D by trimester
1st trimester (250 IU) CVS Miscarriage TOP Ectopic
2nd and #rd (625IU) Obs haemorrage Amnio, cordocentesis ECV Abdo trauma
Prophylaxis: 28 and 34 (625IU)
Why does Kell kill
Dual mechanism of fetal anaemia
- hemolysis form IgG antibodies crossing the placenta
- fetal bone marrow erythropoietin suppression leading to an aplastic anaemia
Approach if antibody screen positive
Determine antibody type
Do titre
Past Obs his
Determine paternal zygosity - if homozygous, child will be affected, if heterozygous 50% chance —> do NIPS
If subsequent pregnancy with high risk of fetal anaemia then screening should be
MCA PSVs from 16-18 weeks
Anti D dosing
Before 12/40 250IU
After 12/40 and PP 625IU
If further event after 2 weeks at any gestation- give further dose
If less than 2 weeks bu more than 20 weeks gestation - for another dose
Ongoing intermittent bleeding after 12 weeks - give anti-D at 2 weekly intervals
