Thrombocytopenia at birth in neonates with red cell alloimmune haemolytic disease

Objective To evaluate the incidence and severity of and risk factors for thrombocytopenia at birth in neonates with red cell alloimmunization. Study design All neonates with haemolytic disease of the foetus/newborn (HDFN) due to red cell alloimmunization admitted to our centre between January 2000 and September 2010 were included in this retrospective study. We measured platelet counts at birth and determined the incidence of thrombocytopenia (platelet count < 150 × 10(9) /l) and severe thrombocytopenia (platelet count < 50 × 10(9) /l). Risk factors for thrombocytopenia at birth were evaluated. Results Thrombocytopenia was present in 26% (94/362) of included neonates with HDFN at birth. Severe thrombocytopenia was found in 6% (20/362) of neonates. Three risk factors were found to be independently associated with thrombocytopenia at birth: treatment with intrauterine red cell transfusion (IUT) (OR 3·32, 95% CI 1·67-6·60, P = 0·001), small for gestational age (SGA) below the 10th percentile (OR 3·32, 95% CI 1·25-8·80, P = 0·016) and lower gestational age at birth (OR 1·22/week, 95% CI 1·02-1·44, P = 0·025). Conclusions Thrombocytopenia at birth occurs in 26% of neonates with HDFN due to red cell alloimmunization and is independently associated with IUT treatment, SGA and lower gestational age at birth