Autoimmune conditions of pregnancy Flashcards
what is a maternal isoantibody/alloantibody and give some clinical examples?
antibodies against an antigen that the mother DOES NOT have
–> Implication= No deleterious effects to the mother but may be lethal to the foetus
Red cell iso-immunisation
Perinatal allo immune thrombocytopenia
perinatal allo-immune neutropenia
what is a maternal auto-antibody and give some clinical examples?
auto-antibody against an antigen the mother HAS herself
thyroid autoimmune disease–> congenital hyperthyroidism
SLE–> lupus like rash in child and FTT
ITP–> thrombocytopenia in the fetus
Sjogren’s disease–> congenital heart block and cardiomyopathy
what are the sites of spontaneous haemorrhage in a fetus with alloimmune thrombocytopenia?
intracranial haemorrhage
GIT
what is the main squelae of alloimmune neutopenia in a baby?
overwhelming bacterial sepsis
what happens if you give WCC to a baby with alloimmune neutropenia?
graft vs host disease
Which red cell antigens can be potentially harmful?
Rhesus D d etc kell kid duffy MNS
presence of anti-duffy/kid antibodies etc will result in haemolysis
how might severe haemolysis result in neonatal cardiac failure?
rate of haemolysis exceeds> EPO production–> anaemia–> hydrops (cardiac failure)
how might we predict the severity of red cell isoimmunisation reaction?
look at the level of antibody (titre)
the lower the titre, the less severe
the higher the titre, the more severe
so this is a good tool for risk assessment
when do we give prophylactic anti-D antibodies?
administered routinely at 28 and 34 weeks of gestation
And at other times of sensitisation:
Before 20 wks= miscarriage/abortion, ectopic pregnancy, amniocentesis/CVS
After 20 weeks= antepartum haemorrhage, DELIVERY!!!
or spontaneous occult bleeding and trauma such as MVA at any time during pregnancy
how might a mother obtain auto-antibodies from antigen exposure from fetus?
blood transfusion
maternal-fetal transfusion
what is the most sensitive way of detecting hypovolemia in a child?
postural hypotension
what is the basic pathophysiology of rhesus isoimmunisation?
Rh-ve mother is exposed to blood from Rh+ve fetus –> produces antibodies to rhesus antigens (IgM to IgG)–> IgG crosses the placenta and contact the RBC of Rh+ve fetus
what is the percentage of pregnant women screened at their first antenatal visit who are found to be Rh-ve?
1%
what percentage of Rh-ve pregnant women have anti-D antibodies?
85%
what are the two extremes of red cell isoimmunisation reaction?
mild jaundice (mildest form)
hydrops foetalis secondary to anaemia causing cardiac failure (most severe form)
what does isoimmunisation refer to?
Where an antibody crosses the placenta and is directed against an antigen that the fetus possesses but not the mother
what potential effect does maternal Sjogren’s syndrome have on the fetus?
fetal heart block
what antibody is associated with anti-phospholipid syndrome?
anti-cardiolipin
what type of antibody (IgM or IgG) can cross the placenta?
IgG
how many babies get mild/moderate/severe forms of red cell isoimmunisation reactions?
mild= 50%
moderate = 25%
severe = 25%
a woman with duffy negative blood urgently requires blood and receives duffy positive blood. what happens?
nothing.
but sensitisation will occur causing antibody production to duffy antigen, so next time she receives duffy positive blood she will have a massive transfusion reaction
how might a pregnant mother become sensitised to a foriegn antigen? (i.e. how might a maternal isoantibody form?)
blood transfusions and IVDU
maternal fetal haemorrhage/mixing of blood from previous pregnancies
at the first antenatal visit, you do a screen for red cell antibodies and find the pregnant woman is Rh D negative. what must you do ix-wise?
- Look at the anti-D antibody titre to assess risk/severity
- Screen the partner!!!
If also Rh-negative then fetus NOT at risk of isoimmunisation reaction.
If Rh-positive, may either be homozygous DD or heterozygous Dd.
what type of blood do we ideally give ALL women of child bearing age during a blood transfusion to avoid future red cell isoimmunisation complications?
should give D negative, Kell negative blood!
how long do we have post delivery to give anti-D antibodies if required to the mother?
up to 72 hours! so three days
which is more common; ABO or rhesus incompatibility between mother and child? what is the prognosis of both?
ABO is 3 x more common than rhesus incompatibility.
ABO incompatibility usually results in mild jaundice but almost never in anaemia or fetal death. so much better prognosis than rhesus incompatibility
what is your antenatal management of low risk red cell immunised pregnancies?
- Antibody titre level at each visit to monitor for maternal-fetal haemorrhage (look for rising titre)
- Continue with current model of care.
- Deliver no later than 38 weeks to prevent prolonged jaundice
what is your antenatal management of moderate risk red cell immunised pregnancies?
- Antibody titre level at each antenatal visit.
- Refer to specialist maternal service!
- Measure the ultrasound flow through the MCA (middle cerebral artery) from 20 weeks. If anaemia is present, then blood systolic velocity through MCA will increase.
- CTG from 32 weeks.
- Deliver at 38 weeks or earlier if fetal anemia present
what is your antenatal management of high risk red cell immunised pregnancies?
- U/s screening from 17 weeks
- Refer to specialist maternal service
- Fetal blood Sampling-if partner is heterozygous to determine whether baby has offending antigen
- Intrauterine transfusions if fetal anaemia present (can give maternal RBC minus the plasma bc it contains the antibodies but not ideal as you can’t keep on bleeding the woman during pregnancy)
- Delivery is indicated when risk of fetal transfusions outweighs the benefits
how might we determine whether the fetus has the D antigen if the partner of a rhesusD negative woman is heterozygous for D antigen (i.e. Dd)?
via aminocentesis (prefer not due to risk of sensitisation event) or
fetal DNA sourced from maternal blood (preferred for DNA analysis)
what blood test do we do to test for fetal maternal haemorrhage?
Kleihauer–Betke test - measures the amount of foetal blood in maternal blood
how might we assess for anaemia in a fetus at high risk of anaemia?
continuous CTG or measurement of MCA (middle cerebral artery) fortnightly and then weekly during the 3rd trimester
at what anti-D antibody titre in the maternal blood is concerning for increased risk of fetal anaemia?
> 1:16 titre
or 4 fold increases in antibody titre such as 1:16 to 1:64
what is the significance of maternal anti-kell antibodies?
any titre of anti-kell antibodies in maternal blood –> risk of fetal anemia in kell +ve babies
why is it important to quantify the amount of foetal maternal haemorrhage in a sensitising event for a rhesus-negative mother?
important to quantify bc higher levels of FMH requires higher doses of passive anti-D immunisation for the mother
how frequent should we be checking the anti-D antibody levels in a rhesus-negative mother during her pregnancy?
monthly blood tests watching for any change in titre levels as titre levels often dictate risk of foetal anaemia
what are the anti-d titre cut off levels for mild/moderate/high risk rhesus disease pregnancies?
mild= > 16
moderate= >64
high risk= > 512
when do we begin to monitor MCA waveforms on fetal uss doppler for pregnancies at risk of rhesus disease?
from 20 weeks gestation
what are the doses of anti-D immunoglobulin that we administer to rhesus negative women?
First trimester (dose 250 IU)
- Chorionic Villus Sampling;
- Miscarriage;
- Termination of pregnancy (either medical or surgical);
- Ectopic pregnancy
Second and third trimester (basic dose 625 IU)
- Obstetric haemorrhage;
- Amniocentesis, cordocentesis;
- External cephalic version of a breech presentation, whether successful
- Abdominal trauma, or any other suspected intra-uterine bleeding or sensitising event.
All Rh (D)-negative women (who have not actively formed their own Anti-D) should be offered a prophylactic dose of 625 IU at approximately 28 weeks gestation and again at approximately 34 weeks gestation.
All women who deliver an Rh (D)-positive baby should have quantification of fetomaternal haemorrhage to guide the appropriate dose of anti-D prophylaxis, and the dose should be given within 72 hours if possible.
