RHESUS INCOMPATIBLE PREGNANCY

Question 1

% of whites, blacks and Asians that are RH negative

Answer 1

Whites - 15%
Blacks - approx, 6%
Asians - <1%

Question 2

% prevalence of Rh D negativity in pregnancy in Nigeria

Answer 2

4.5 - 5.5%

Question 3

How many ml of Rh D positive blood can cause sensitization

Answer 3

< 1ml

Question 4

T/F: With sensitization, all Rh D negative women become isoimmunized

Answer 4

F
30% of rhesus D-ve will not be isoimmunized despite sensitization

Question 5

% of Rh D negative women that will not be isoimmunized despite sensitization

Answer 5

30%

Question 6

After sensitization how long does it take for antibodies in maternal blood to reach equilibrium in fetal circulation

Answer 6

1 month

Question 7

How many antigens are in the rhesus system

Answer 7

61

Question 8

The 5 major types of antigens in the rhesus system that can cause significant transfusion reactions are

Answer 8

C, c, D, E, e and anti-kell

Question 9

List the 5 antigens of the rhesus system in the order of decreasing immunogenicity

Answer 9

D>c>E>C>e

Question 10

T/F: Anti-D antibody is the most common cause of haemolytic dx

Answer 10

T in most countries

Question 11

4 in-utero effects of Rh isoimmunization on the fetus

Answer 11

Hyperbilirubinaemia
Fetal anaemia
Hydrops fetalis
Intrauterine fetal death

Question 12

4 short term effects of Rh isoimmunization in neonatal life

Answer 12

Neonatal jaundice
Neonatal anaemia
Early neonatal death
Hyporegenerative anaemia
(Hyporegenerative anaemia due to transient suppression of erythropoiesis, common with multiple in-utero transfusions)

Question 13

2 long term effects of Rh isoimmunization on the baby

Answer 13

Brain damage
Sensorinueral deafness

Question 14

9 potential sensitizing events for Rh disease

Answer 14

1. Miscarriage
2. Termination of pregnancy
3. Antepartum haemorrhage
4. Invasive prenatal testing e.g.
   CVS, amniocentesis,
   cordocentesis
5. Fetal medicine procedures e.g.
   shunt insertions
6. Delivery
7. External cephalic version
8. IUFD
9. Abdominal trauma

Question 15

3 factors determining risk of sensitization

Answer 15

1. Volume of fetomaternal blood
   exchanged
2. Maternal immune response
3. Concurrent ABO incompatibility

Question 16

What is the routine prophylactic management of unsensitized Rh negative women in pregnancy

Answer 16

Blood for Rh antibodies at 28 & 34wks before anti-D

Question 17

Outline with 4 points the antenatal management of unsensitized Rh D negative women using free fetal DNA

Answer 17

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

Question 18

T/F: To prevent isoimmunization Anti-D prophylaxis should be given within 72 hours of any sensitizing event

Answer 18

T

Question 19

The test used to estimate the degree of fetomaternal haemorrhage (FMH)

Answer 19

Kleihauer Betke test

Question 20

T/F: Kleihauer Betke test can be used to calculate the amount of anti D to be given

Answer 20

T

Question 21

What is the prevalence of massive fetomaternal haemorrhage at delivery

Answer 21

1/1000 deliveries

Question 22

At what GA should anti D be given prophylactically

Answer 22

28 weeks and 34 weeks

Question 23

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

Answer 23

T

Question 24

T/F: Once sensitized, it is not reversible with anti-D

Answer 24

T

Question 25

T/F: Rhesus disease gets worse with successive pregnancies

Answer 25

T

Question 26

How often should you monitor antibody levels in an already sensitized pregnant woman

Answer 26

every 4 weeks from booking till 28 weeks, then 2-weekly till delivery

Question 27

T/F: Antibody titre - does not correlate well with development of HDFN

Answer 27

T

Question 28

HDFN is unlikely at what level of antibody titre

Answer 28

< 4 IU/ml

Question 29

At what level of antibody titre is the risk of HDFN moderate

Answer 29

4 – 15 IU/ml

Question 30

At what level of antibody titre is the risk of hydrops fetalis very high

Answer 30

>15 IU/ml

Question 31

With high antibody, 2 methods of checking for fetal anaemia

Answer 31

Bilirubin concentration in amniotic fluid Middle cerebral artery doppler (MCA) peak velocity measurement – increased risk of anaemia if raised

Question 32

At what GA will you deliver an already sensitized woman

Answer 32

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

Question 33

4 methods of in utero blood transfusion

Answer 33

Intra-umbilical Intrahepatic Intraperitoneal Intracardiac

Question 34

6 qualities of blood that should be used for in utero transfusion

Answer 34

1. Rh negative 2. Crossmatched with maternal blood' 3. Densely packed (30g/dl) 4. Irradiated 5. CMV negative 6. White cell depleted

Question 35

T/F: For all Rh-ve mothers, take cord blood at delivery for FBC, blood group and indirect Coomb’s test

Answer 35

T

Question 36

T/F: All women should have their blood group and antibody status determined at booking and at 28 weeks of gestation

Answer 36

T

Question 37

Timing of delivery for women with red cell antibodies that can cause fetal anaemia will depend on --, -- and --

Answer 37

The antibody levels/titres The rate of rise of antibodies History of having had any fetal therapy in index pregnancy