Paving the way for improved management of severe immune thrombocytopenia purpura in pregnancy.

Abstract

Those of us who take care of women with blood disorders have few data on which to base our management of thrombocytopenia in pregnancy, particularly immune thrombocytopenia purpura (ITP). We extrapolate from the management of ITP in non-pregnant individuals and try to raise platelet counts in an attempt to meet the bleeding challenges of childbirth. Thirty years ago we believed that ITP conferred fetal risks similar to those conferred by alloimmune thrombocytopenia. Experience and small series have taught us otherwise, but fetal let alone maternal risks have not been well quantified. Care et al. have provided us with data from the largest series of ITP patients in pregnancy to date. Using the UK Obstetric Surveillance System (UKOSS), which has been developed to study rare disorders in pregnancy, the investigators identified pregnant women with severe ITP from 1 June 2013 through to 31 January 2015. Rather than researching the diagnosis, the investigators adopted a practical definition of severe ITP, which included: (1) thrombocytopenia with a nadir platelet count of <50 × 109 l−1 after obstetric and hereditary causes had been excluded; or (2) thrombocytopenia that was treated. All 202 UK hospitals with consultant-led maternity units were queried monthly. The investigators reported on the incidence of severe ITP in pregnancy, current management, and the maternal and fetal outcomes of pregnancy. They estimated that the incidence of severe ITP in pregnancy is 1 in 10 000 pregnancies. They found that outcomes for neonates were better than expected, with no cases of intracranial haemorrhage or death. They found that there were no cases of epidural, caesarean section wound, or perineal haematoma following delivery. They also found that severe ITP in pregnancy carries a high risk of severe postpartum haemorrhage. Although this was an observational as opposed to a randomised study, the treated and untreated groups were comparable, with no difference in the lowest platelet count prior to pregnancy. Treatment [with steroids, intravenous immunoglobulin (IVIG), or both] appeared to make no difference in either maternal or fetal outcomes. These findings are surprising. Perhaps we should not be surprised that fetal outcomes were good because, in theory, maternal autoantibodies should not significantly impact fetal platelets. More surprising, however, is that the rate of postpartum haemorrhage was five times higher than estimates from the literature, and that treatment of severe ITP in pregnancy, which is targeted at raising platelet counts to achieve a ‘safe’ threshold in pregnancy or to achieve a target platelet count for delivery, appears to be ineffective in protecting women with severe ITP from postpartum haemorrhage. By providing us with evidence for this rare disorder, the investigators have paved the way for improving the management of severe ITP in pregnancy. They have shown us that existing treatments, which may improve platelet counts, may not improve platelet function, and do not appear to reduce the high risk of postpartum haemorrhage. Randomised trials in rare disorders are often not feasible, but it is time to consider alternative treatments and alternative study designs to capture the results of such treatments. None declared. Completed disclosure of interests form available to view online as supporting information. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.