Screening of pregnant women to reduce fetal and neonatal alloimmune thrombocytopenia (FNAIT)

Aim: Present updated results from the large prospective screening study for neonatal alloimmune thrombocytopenia that was published in Blood in 2007.¹

Method: In 100,448 pregnancies human platelet antigen (HPA)-1 typing was performed and HPA 1bb women with anti-HPA-1a antibodies were followed-up during pregnancy and delivered by caesarean section (CS) in week 36 – 38. Compatible platelets were available for immediate transfusion to the newborn. The results were compared with historical controls.

Result: The results from our previously published study¹ showed that there was a significant reduction of intracranial haemorrhage (ICH) and stillbirth when identification of pregnancies at risk and clinical follow-up was performed. There were two cases of ICH and 1 stillbirth in the treatment group as opposed to seven cases of ICH and three stillbirths in the control studies. The three severe cases of FNAIT¹ were included in the large “No Intra Cranial Haemorrhage (NOICH) registry” which is a multinational registry including almost 600 pregnancies complicated by FNAIT from 13 centres across the world ². To determine the accurate time of bleeding in foetuses in the NOICH registry² the scans were re-evaluated by an expert in neuroradiology, and surprisingly, there was no evidence of ICH in one ICH case identified by the screening program. This means that the relative risk of serious complications was reduced from 0.27 (95% CI: 0.08 to 0.92) to 0.18 (95% CI: 0.05 – 0.6) when compared with historical controls.

Conclusion: This data further support the importance of screening pregnant women in order to reduce anti-HPA-1a antibody induced bleeding complications. Further, a screening program would help identify unimmunized pregnant women who could benefit from prophylactic treatment.

References:

(1) Kjeldsen-Kragh J et al. Blood 2007; 110(3):833 – 839.

(2) Tiller H et al BMJ Open 2013; 3(3).