RHESUS INCOMPATIBILITY

Rhesus isoimmunization occurs in pregnancy where a Rhesus-negative mother is pregnant with a Rhesus-positive foetus. Other ways of isoimmunization include transfusion with Rhesus incompatible blood, ectopic pregnancy, hydatidiform mole, and abortion.

Clinical Features

  • Usually none
  • Severe isoimmunization can lead to;
    • Spontaneous abortion
    • Intrauterine foetal death (hydrops foetalis)
    • Neonatal death.

Severely affected neonates who require exchange transfusion need to be referred for appropriate management to avoid hyperbilirubinaemia.

Investigations

  • Blood groups and Rhesus factor in all pregnant women.
  • Rhesus status of husbands of women who are Rh-negative. If he is Rh negative, then the foetus should be Rh-negative and hence no risk of isoimmunization in the mother. Do remember, however, that extramarital pregnancies do occur.
  • Rhesus antibody screening in those who are Rhesus-negative (i.e., indirect Coombs’ test) as soon as possible and every month starting at 20 weeks.
  • If Rhesus antibody titre is above 1:8 then do amniocentesis for bilirubin spectrophotometry. The results of this are read on the Liley’s graph and the pregnancy managed accordingly.

Management with Obstetrician and Paediatrician

Pregnancies that are severely affected while the foetus is premature can benefit from intrauterine transfusion. Rhesus disease should be managed by an obstetrician.

Prevention

  • A Rh-negative woman who delivers a Rh-positive baby must have anti D 500mcg IM within 72 hours of delivery if they are not already isoimmunized (i.e., Rh antibody negative or negative indirect Coombs test, or rhesusnegative
    baby)
  • The same applies for un-isoimmunized Rh-negative mothers who have an abortion, ectopic pregnancy, hydatidiform mole, or obstetric amniocentesis.