Allo-immunisation Flashcards
1
Q
Discuss anti-D in pregnancy
-Who should get it
-When should they get it
-What doses should be given
-Timing of Anti-D
-Testing required around doses
A
- Who should get it
-Anti-D should be given to Rh- women who do not have Anti-D antibodies
-Can do NIPT from 11/40 for Rh status. If Rh neg then no AN prophylaxis required - When should it be given
First trimester
-Threatened miscarriage >12 weeks
-Ectopic pregnancy
-Termination - medical (>10/40) or surgical
-Miscarriage
-Molar pregnancy
Second trimester
-CVS
-APH >12 weeks
-Amniocentisis
-ECV
-Abdo trauma
-Prophylaxis for silent sensitisation 28 and 34 weeks - What doses should be given
-First trimester 250IU
-13-20 weeks 625IU for prophylaxis no kleihauer required
->20 weeks 625IU + kleihauer to determine if additional is required in sensitising events
-Multiple pregnancy 625IU in any trimester
-No evidence for higher dose in women with BMI >30 - Timing of anti-D
-Within 72hrs but effective up to 10 days
-If ongoing PVB then repeat dose at 6 weeks - Test prior to anti-D
-Check for anti-D antibodies before giving anti D unless has 28 prophylactic dose
-Postnatally to work out dose
-Prior to sensitising event if >20 weeks
-Test 48hrs post anti-D delivery in large FMH <6mL to determine if further is required
2
Q
How effective is prophylactic anti-D at stopping alloimmunisation (3)
A
-Cochrane - 78%
-NICE - 70%
- Anti D 500IU at 28 and 34 weeks reduces risk from 1% to 0.35%
3
Q
What are the antibodies involved with HDFN
-Which ones have the greatest risk of HDFN (3)
-Which ones have moderate risk of HDFN (5)
A
- Highest risk
-Anti-D, Anti c, Anti-K (Kell) - Moderate risk
-Anti Fy, Anti jk, Anti E, anti C and Anti Ce - Anti A and Anti B antibodies can develop in an O mother and cross the placenta causing mild to moderate anemia
4
Q
Discuss red cell antibodies
-Pathophysiology
-Incidence
-Fetal and neonatal consequence
A
- Pathophysiology
-Development of IgG antibodies to antibodies on the fetal RBC causing destruction of fetal blood cells
-Results from exposure to RBC antigens in previous pregnancies, transplantation or blood transfusions
-Risk of antibodies to current pregnancy low as IgM takes up to 12 weeks to convert to IgG which can cross the placenta - Incidence
-1% of pregnant women have anti RBC antibodies
-0.4% of pregnancies have clinically significant RBC antibodies
-Most common RBC antibody is anti-D
-Anti-K is the second most common antigen - Fetal and neonatal consequences
-Fetal anaemia
-Hydrops fetalis secondary to high output heart failure
-Jaundice and neurological impairment from high bilirubin levels from haemolysis
5
Q
How should anti-D HDFN be managed
-Antenatal management (8)
-Delivery (4)
A
- Antenatal management
-Women with anti-D antibodies should undergo titres
-Titres should be done monthly to 28/40 then fortnightly until delivery
-Titres <4IU/mL have low risk of HDFN, titres 4-15 have moderate risk and titres >15 have high risk. Ref to MFM
-Check father to see if Rh- (If Rh neg then no further action)
-Check ffDNA if shows fetus Rh -ve then no further action
-If Risk significant for HDFN (>4IU/mL) then weekly scans for MCA PSV 1.5 MoM suggests moderate/severe anemia
-Intrauterine blood transfusion if required - Delivery
-Deliver no later than 37/40
-Mode of delivery to be individualised
-Continuous CTG
-Neonatal team to be aware with transfusions ready
6
Q
Discuss anti-Kell HDFN
-Incidence
-Impact on fetal RBC
-Significance of titre
A
- Incidence
-0.1-0.2% alloimmunisation
-Most cases from transfusion of Kell + blood - Impact on fetal RBC
-Suppression of RBC production
-Haemolysis - Significance of titre
-Titre doesn’t correspond to severity of anaemia so can’t stratisfy risk of HDFN
7
Q
Discuss management of anti-Kell alloimmunisation
-Antenatal
-Delivery
A
- Antenatal management
Once Anti-Kell identified:
-check father for Kell if negative then no further action
-check ffDNA and if negative then no further action
If Kell positive for either fDNA or father
-Refer to MFM regardless of titre level
-Titre levels monthly till 28 weeks then fortnightly until delivery
-Weekly scans for MCA-PSV
-Intrauterine transfusion as required - Delivery
-Delivery no later than 37/40
-Mode of delivery to be individualised
-Neonatal team aware for possible transfusion
-Continuous CTG
8
Q
Discuss management of Anti-c alloimmunisation
-Antenatal management
-Delivery
A
- Antenatal management
-Titres should be done monthly to 28/40 then fortnightly until delivery
-Titres <7.5IU/mL have low risk of HDFN, titres 7.5-20 have moderate risk and titres >20 have high risk. Ref MFM
-Check father to see if Rh- (If Rh neg then no further action)
-Check ffDNA if shows fetus Rh -ve then no further action
-If Risk significant for HDFN (>7.5IU/mL) then weekly scans for MCA PSV - 1.5 MoM suggests moderate/severe anemia
-Intrauterine blood transfusion if required - Delivery
-Deliver no later than 37/40
-Mode of delivery to be individualised
-Continuous CTG
-Neonatal team to be aware with transfusions ready
9
Q
Discuss anti-c antibody
-Impact on fetus
-Association with anti-E
A
- Impact on fetus
-Up to 20% of babies with anti-c mothers require transfusion
-Can cause delayed anemia - Association with anti-E
-The presence of anti-E can make fetal anaemia worse and so referral to specialist should be made at lower titre levels
10
Q
Discuss management of RBC antibodies that have moderate risk of HDFN
A
- Screen at AN bloods and repeat testing at 28 weeks
- Further evaluation of titres should be individualised
- Women with anti-E antibody titre >1:32 should be evaluated for fetal anaemia with MCA-PSV 1-2 weekly
- Refer women to MFM with a titre > 32, Significant Hx of HDFN or Intrauterine transfusion.
