Paediatrics: Rh disease (rhesus haemolytic disease)

Rh disease (rhesus haemolytic disease)

Haemorrhage of foetal blood of differing rhesus group into the maternal circulation leads to maternal anti-D IgG production (usually foetus RhD +ve, mother RhD –ve). Transplacental passage of this antibody leads to foetal RBC haemolysis. The condition is usually asymptomatic or only mild in the first affected pregnancy. Severity usually increases with subsequent pregnancies. Maternal blood group and rhesus antibody status are routine-ly checked in early pregnancy. Elevated or rising titres indicate that further foetal investigation is warranted, e.g. serial anti-Rh titres, foetal US, foetal blood sampling. The risk of disease is predicted by maternal anti-Rh titre:

•   Unlikely when maternal anti-Rh titre <4u/mL.

•   10% when titre is 10–100u/mL.

•   70% when foetal Hb <7g/dL or titre >100u/mL.

Iso-immunization may also occur with other blood group incompatibilities, (e.g. ABO—usually baby A or B and mother O), other rhesus groups (e.g. c, C, e, E), Kell, Kidd, Duffy. Clinical presentation is usually milder than with RhD (particularly ABO).

Presentation

•   Antenatal: foetal anaemia, hydrops foetalis.

•   Postnatal: hydrops foetalis, early jaundice, kernicterus, cutaneous haemopoietic lesions (‘blueberry muffin’), hepatosplenomegaly, coagulopathy, thrombocytopenia, leucopenia. Late: anaemia, inspissated bile syndrome.

Investigations

•   Maternal blood for: group (usually RhD –ve), ‘rise’anti-Rh titre.

•   Initially, cord or neonatal blood for: ‘fall’ Hb, ‘rise’reticulocytes, ‘fall’ platelets, DCT +ve, group (usually RhD +ve), ‘rise’SBR.

•   After diagnosis monitor SBR 4-hourly (until rate of rise known), blood glucose, rate of Hb fall. Check coagulation screen.

Treatment

•   Close antenatal supervision +/– intrauterine blood transfusion.

•   After birth check cord SBR and Hb, start high risk infants on intensive phototherapy whilst awaiting results. If SBR>100µmol/L then prepare infant for exchange transfusion, consider IVIG.

•   Supportive treatment as required, e.g. correct any coagulopathy.

•   If treatment required, oral folic acid 250mcg/kg/day for 6mths.

•   Check Hb every 1–2wks to detect anaemia for up to 12wks. Transfuse if symptomatic or Hb <7g/dL.

•   Perform audiology screening if exchange transfusion required.

•   Prophylaxis: Rh anti-D IgG given to RhD –ve mothers after birth of Rh +ve foetus or possible foeto-maternal haemorrhage.

Prognosis

Mortality <20% even if hydropic. Risk of late onset anaemia.