RHESUS INCOMPATIBLE PREGNANCY Flashcards
% of whites, blacks and Asians that are RH negative
Whites - 15%
Blacks - approx, 6%
Asians - <1%
% prevalence of Rh D negativity in pregnancy in Nigeria
4.5 - 5.5%
How many ml of Rh D positive blood can cause sensitization
< 1ml
T/F: With sensitization, all Rh D negative women become isoimmunized
F
30% of rhesus D-ve will not be isoimmunized despite sensitization
% of Rh D negative women that will not be isoimmunized despite sensitization
30%
After sensitization how long does it take for antibodies in maternal blood to reach equilibrium in fetal circulation
1 month
How many antigens are in the rhesus system
61
The 5 major types of antigens in the rhesus system that can cause significant transfusion reactions are
C, c, D, E, e and anti-kell
List the 5 antigens of the rhesus system in the order of decreasing immunogenicity
D>c>E>C>e
T/F: Anti-D antibody is the most common cause of haemolytic dx
T in most countries
4 in-utero effects of Rh isoimmunization on the fetus
Hyperbilirubinaemia
Fetal anaemia
Hydrops fetalis
Intrauterine fetal death
4 short term effects of Rh isoimmunization in neonatal life
Neonatal jaundice
Neonatal anaemia
Early neonatal death
Hyporegenerative anaemia
(Hyporegenerative anaemia due to transient suppression of erythropoiesis, common with multiple in-utero transfusions)
2 long term effects of Rh isoimmunization on the baby
Brain damage
Sensorinueral deafness
9 potential sensitizing events for Rh disease
- Miscarriage
- Termination of pregnancy
- Antepartum haemorrhage
- Invasive prenatal testing e.g.
CVS, amniocentesis,
cordocentesis - Fetal medicine procedures e.g.
shunt insertions - Delivery
- External cephalic version
- IUFD
- Abdominal trauma
3 factors determining risk of sensitization
- Volume of fetomaternal blood
exchanged - Maternal immune response
- Concurrent ABO incompatibility
What is the routine prophylactic management of unsensitized Rh negative women in pregnancy
Blood for Rh antibodies at 28 & 34wks before anti-D
Outline with 4 points the antenatal management of unsensitized Rh D negative women using free fetal DNA
Free fetal DNA at 15 – 16wks
FBC and Rh antibodies at 28wks regardless of FFDNA results
Fetus positive
Give Anti-D 1500iu stat
Fetus negative
Do not give Anti-D
T/F: To prevent isoimmunization Anti-D prophylaxis should be given within 72 hours of any sensitizing event
T
The test used to estimate the degree of fetomaternal haemorrhage (FMH)
Kleihauer Betke test
T/F: Kleihauer Betke test can be used to calculate the amount of anti D to be given
T
What is the prevalence of massive fetomaternal haemorrhage at delivery
1/1000 deliveries
At what GA should anti D be given prophylactically
28 weeks and 34 weeks
T/F: Administration of 1dose of 1500iu (300µg) of Anti-D between 28 - 30weeks gestation is as effective at reducing haemolytic disease as 2 doses of 500iu (100µg) at 28 and 34 weeks gestation
T
T/F: Once sensitized, it is not reversible with anti-D
T
T/F: Rhesus disease gets worse with successive pregnancies
T
How often should you monitor antibody levels in an already sensitized pregnant woman
every 4 weeks from booking till 28 weeks, then 2-weekly till delivery
T/F: Antibody titre - does not correlate well with development of HDFN
T
HDFN is unlikely at what level of antibody titre
< 4 IU/ml
At what level of antibody titre is the risk of HDFN moderate
4 – 15 IU/ml
At what level of antibody titre is the risk of hydrops fetalis very high
> 15 IU/ml
With high antibody, 2 methods of checking for fetal anaemia
Bilirubin concentration in amniotic fluid
Middle cerebral artery doppler (MCA) peak velocity measurement – increased risk of anaemia if raised
At what GA will you deliver an already sensitized woman
Aim at delivery at 36- 37 weeks unless there are specific reasons to conduct this earlier, e.g. severe hydrops unresponsive to transfusion or services unavailable
4 methods of in utero blood transfusion
Intra-umbilical
Intrahepatic
Intraperitoneal
Intracardiac
6 qualities of blood that should be used for in utero transfusion
- Rh negative
- Crossmatched with maternal
blood’ - Densely packed (30g/dl)
- Irradiated
- CMV negative
- White cell depleted
T/F: For all Rh-ve mothers, take cord blood at delivery for FBC, blood group and indirect Coomb’s test
T
T/F: All women should have their blood group and antibody status determined at booking and at 28 weeks of gestation
T
Timing of delivery for women with red cell antibodies that can cause fetal anaemia will depend on –, – and –
The antibody levels/titres
The rate of rise of antibodies
History of having had any fetal therapy in index pregnancy
