Transfusion in Pregnancy

Pregnancy changes blood volume and haemoglobin, increases the risk of haemorrhage and exposes the mother to foetal red cells, which can cause alloimmunisation. Transfusion in pregnancy must protect the mother and avoid immunising her against antigens that could harm this or a future foetus.

Physiological anaemia. Plasma volume expands more than red cell mass, so haemoglobin falls. Anaemia in pregnancy is usually defined as haemoglobin under 11 g/dL in the first and third trimesters and under 10.5 g/dL in the second. Severe anaemia is under 7 g/dL.

Alloimmunisation. The commonest clinically important antibodies are anti-D, anti-K, anti-c and anti-E. Anti-D causes severe haemolytic disease of the foetus and newborn. Anti-K suppresses foetal erythropoiesis, and titres predict severity poorly.

Special groups. Women with sickle cell disease or thalassaemia, previous transfusion, previous affected pregnancy, placenta praevia or accreta, and those who refuse blood. In East Africa, anaemia is common in pregnancy (iron deficiency, malaria, hookworm, HIV, sickle cell disease), so transfusion is a frequent decision and antenatal antibody screening may not be universal.

Transfusion thresholds.

• Haemoglobin under 7 g/dL at any gestation, or higher with symptoms or cardiac decompensation.

• Haemoglobin 7 to 8 g/dL near term (after about 36 weeks) when delivery is near, because of reduced reserve for haemorrhage.

• Ongoing haemorrhage: by clinical state, not haemoglobin.

• Treat iron deficiency with oral or intravenous iron, malaria with treatment and prevention, and hookworm after the first trimester.

Antenatal antibody screening. At booking and again at about 28 weeks, and in any woman with a prior transfusion. RhD negative women receive anti-D prophylaxis at about 28 weeks and after sensitising events, and the passive antibody is expected on screening.

When an antibody is found.

• Identify it, and test the partner or the foetus (cell free foetal DNA genotyping where available).

• Monitor titre every 2 to 4 weeks from the point of detection. A critical titre (usually 1 in 16 or an equivalent concentration, set by the laboratory) triggers foetal assessment. Titre is a poor guide in anti-K.

• Assess foetal anaemia with middle cerebral artery Doppler peak systolic velocity, with values over 1.5 multiples of the median suggesting moderate to severe anaemia.

Intrauterine transfusion indications. Severe foetal anaemia (Doppler criteria or foetal haemoglobin under about 0.65 multiples of the median), usually before 35 weeks, by a foetal medicine specialist.

Red flags. Hydrops, rising titre, history of a previously affected baby and abnormal Doppler.

Transfusion in the mother.

• Red cells that are leucodepleted, cytomegalovirus safe, K negative and, for RhD negative women, RhD negative. Antigen negative cells are provided for any antibody found.

• One unit at a time, reassessing, at 1 mL/kg/hour or slower with cardiac disease, hypertension or pre-eclampsia.

• Left lateral tilt in late pregnancy, and monitor the foetus.

• Do not use anti-D immunoglobulin to treat an established anti-D.

Intrauterine transfusion. Group O RhD negative (and K negative) red cells, irradiated, cytomegalovirus safe, fresh (under about 5 days), with a haematocrit of about 75 to 80%, given by intravascular route by a foetal medicine specialist, with repeat transfusions at intervals set by the specialist.

Delivery planning. Timing set by the foetal medicine team (often 37 to 38 weeks for affected pregnancies), and a neonatal team ready for exchange or phototherapy. For placenta praevia or accreta, plan delivery in a centre with a blood bank, cell salvage, interventional radiology and a surgical team, with crossmatched blood available (usually 4 or more units) and fibrinogen replacement ready.

Sickle cell disease and thalassaemia. Prophylactic transfusion is considered in sickle cell disease with complications, and regular transfusion continues in transfusion dependent thalassaemia, with matched blood and iron chelation adjusted (deferasirox and deferiprone are avoided in pregnancy).

Postnatal. Check the baby's group and direct antiglobulin test, give anti-D immunoglobulin to RhD negative mothers of RhD positive babies within 72 hours, and test for foetomaternal haemorrhage.

Special groups.

• Women refusing blood: early anaemia optimisation with intravenous iron and erythropoiesis stimulating agents, cell salvage and tranexamic acid, and documented plans.

• Hypertensive disease: careful volume management.

Monitoring. Maternal vital signs, haemoglobin, antibody titres, foetal wellbeing, Doppler and fluid balance.

Complications. Circulatory overload and pulmonary oedema (especially with pre-eclampsia), transfusion reactions, alloimmunisation to new antigens, foetal hydrops, foetal loss, and haemorrhage at delivery.

Referral and escalation. Foetal medicine specialist for any significant antibody, haematologist and blood bank for antigen negative blood, and anaesthetist for planned high risk delivery.

Disposition. Document the antibodies and give the woman a written record for future pregnancies. Arrange a neonatal plan, postnatal iron therapy and follow up of the baby for late anaemia.