Essay 301 - Rhesus disease

Antenatal amangement depends on Rh status of fetus  which can be determined by cell free fetal DNA in maternal circulation.Partners genotype for Rh  determined.If partner is cde,cde RH negative  and of confirmed paternity,fetus can be asumed to be Rh negative and is not at risk.However if genetic father is cde,cD e fetus has 50% chances it may be Rh + and if cDe cDe , fetus is 100% Rh+.After confirming fatal Rh status from Maternal Cell free DNA / monitering for fetal MCA velocity to detect Fetal anemia from 28 weeks gestation every 2weekly or more frquently if severely  affected  is required. Inutero transfusion with O Rh neg.Kell neg, CMV negative  blood crossmatched against maternal serum is required to prevent fetal anemia , Hydrops and later, hyperbilirubinemia and Kernicterus. Complete exchange transfusion in utero via cord itself can cause  miscarriage, infection and sensitization.Hence written information is provided to mather and partner and information about support  groups given prior to the procedure. Anticipating need to deliver preterm antenatal steroids given to prevent Respiartory distress, Intracranial haemorrhage and Necrotising enterocolitis., drugs causing displacement of bilirubin including aspirin avoided in mother.Time of delivery as per Expert opinion from Fetomaternal unit and treatment undertaken where facilities for in utero transfusion , Nicu bed s and SCBU available in Tertiary level center.Neonatologist informed for further surveillance of baby after delivery to prevent kernicterus and exchange transfusion may be required after delivery.

(b) The national guidelines are not followed strictly. In late booker where early date scan may be discrepancy is SGA or FGR an was missed and fetus ThereSecondly there might be unrecognized sensitizing events during pregnancy. Thirdly the fetomaternal haemorrhage postnatally might be underestimated. Fourthly there might be delayed administration of anti D during pregnancy. Moreover sensitization might take place in subsequent pregnancies and also by events outside of pregnancy like blood transfusion.

A good answer should include

(a)  Antenatal management

MDT care with fetal medicine centre and blood transfusion service

Assess risk of fetus being affected

·      History of previous affected pregnancy

·      Paternal Rhesus genotype – discuss limitations

·      Fetal Rhesus genotype – based on amniocentesis. Discuss limitations

·      Use cell-free DNA in maternal blood. Discuss limitations

Subsequent management dependent on fetal Rhesus type

·      If fetus is Rh negative, reassure

·      If fetus is Rh positive or status uncertain - serial quantification of level of anti-D antibodies. Fetal anaemia rare below 10-15 IU

·      Monitor for fetal anaemia using serial middle cerebral artery Doppler (peak systolic velocity) every 1-2 weeks. High risk of anaemia if >1.5MoM

·      Fetal blood sampling if evidence of anaemia on Doppler

·      Intra-uterine transfusion if haematocrit < 30%

·      Antenatal corticosteroids for fetal maturity

·      Aim for delivery at 34-36 weeks if transfusion has been required or 37-38 weeks if no transfusion needed

·      Antibodies may delay cross-match so blood gouped & saved if in labour / before CS

(b)  Reasons for perinatal morbidity

·      Allo-immunisation to other antigens (Rhesus E / c and other red cell antigens) for which prophylaxis is not available

·      Missed prophylaxis – omitted / delayed in previous pregnancies

·      Failed prophylaxis

·      Occult feto-maternal haemorrhage

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