Red Cell Antibodies in Pregnancy - GT65 Flashcards
Which red cell antigens can be tested for using non-invasive fetal genotyping?
D, C, c, E, K antigens
When would invasive testing be considered for red cell antigens?
If antibodies other than D, C, c, E, K are present
If testing being carried out for other reasons, e.g. karyotyping
When (generally) should patients be referred to FMU if the fetus is at risk of anaemia?
Rising antibody levels/titres
Level/titre above certain threshold (see separate question)
USS suggestive of anaemia
Unexplained severe neonatal jaundice
Neonatal anaemia requiring transfusion or exchange transfusion
When should referral to FMU be taken for patients with antibodies other than anti- D, c and K?
Hx of previous significant HDFN or intrauterine transfusion
Titire >= 32 (especially if rising)
At what level should patients with anti-D antibodies be referred to FMU?
> 4iu/ml
At what level should patients with anti-c antibodies be referred to FMU?
> 7.5iu/ml
At what level should patients with anti-K antibodies be referred to FMU?
At any level - severity does not correlate with titre level
At what level should patients with anti-E antibodies be referred to FMU?
If anti-c also present - potentiates effect; then at lower levels
How often should antibody levels be monitored during pregnancy once anti D, c, and K detected?
Every 4/52 until 28/40
Then every 2/52 until delivery
(Even though K doesn’t correlate)
How often should antibody levels be monitored during pregnancy (Other than D c and K) ?
Retest at 28/40
Unless previous hx of HDFN
Discuss with bloodbank re: testing if crossmatch isssues anticipated (usually weekly if high risk for blood transfusion)
How often should fetal monitoring occur if it has the corresponding antigen or antibody titres reach the required threshold?
And when should invasive treatment be considered?
Weekly ultrasound, especially looking at MCA PSV (peak systolic velocity)
(100% sensitivity - decreases at 36/40 - FPR 12%)
Invasive treatment once MCA PSV rises above 1.5 MoM
What type of donor blood should be used for intrauterine transfusion?
- O or ABO typed
- Negative for the antigens corresponding to maternal antibodies
- K neg
- CMV neg and irradiated last 24 hrs - large vol = GVHD
- <5/7
- In CPD anticoagulant
What type of donor blood should be used for maternal transfusion?
- ABO and D typed
- K neg
- CMV neg
For women with multiple antibodies requiring rare donation - where does frozen blood come from?
National Frozen Blood bank in Liverpool
What type of donor blood should be used for neonatal exchange?
- ABO typed with fetus AND mother
- Rh neg (or typed to fetus)
- K neg and neg for antigen causing anaemia
- <5/7 old
- CMV neg and irradiated (if no time delay for latter)
- Plasma reduced, haematocrit 0.5-6
What type of donor blood should be used for neonatal small volume top up transfusion?
- ABO typed with fetus AND mother
- Rh neg (or typed to fetus)
- K neg and neg for antigen causing anaemia
- <35/7 old
- CMV neg, irradiated if previous IUT (prevent GVHD)
- Stored in SAGM
What cord blood samples should be taken if mum has clinically significant antibodies?
Direct antiglobulin test (DAT)
Hb
BR levels
How many pregnancies have antibodies, and what is the prevalence of clinically significant antibodies?
Antibodies 1.2% pregnancies (1 in 80)
0.4% clinically relevant (1 in 300)
How many cases of anti D alloimmunisation were accounted for by late immunisation in a first pregnancy, prior to routine anti-D prophylaxis?
18-27%
Similar proportion in 2nd/subsequent pregnancies
Which antibodies other than D, c and K can cause significant fetal anaemia?
Anti E, Fy Jk C Ce
What is the perinatal survival for pregnancies with antibodies causing severe anaemia following treatment (hydropic and non-)?
84% overall
Hydropic 74%
Non hydropic 94%
How does anti-K cause fetal anaemia and how does it differ from other antibodies?
Erythroid suppression and immune destruction of early erythroid progenitor cells
Hyperbilirubinaemia not a feature, can occur at relatively low titres
From what gestation can genotyping (cfDNA) be determined?
16/40 for C, c, E, e
20/40 for K
Can’t determine twins
What is the risk of fetal loss following in utero fetal blood sampling?
1-3%, higher if hydropic
If ABO, K, D typed blood not matched for other antibodies is the only option for a life threatening haemorrhage, what other measures can be taken?
Give 1g IV methylpred and resuscitate if necessary, including adrenaline
No implications for plts, FFP, cryoprecipitate or fractionated products
When should women with clinically significant antibodies be delivered?
If stable throughout pregnancy - aim 37-38/40
If IUT performed will depend on how recent - ie deliver when anaemia avoided (not indication for C/S)
CEFM
Why is sensorineural hearing loss more common in infants complicated by haemolytic disease of the newborn?
Toxic effect of prolonged exposure of bilirubin on CNVIII
