Severe primary autoimmune thrombocytopenia in pregnancy: a national cohort study.

OBJECTIVE: To quantify the incidence of severe autoimmune thrombocytopenia (ITP) in pregnancy in the UK, determine current treatment strategies, and establish maternal and neonatal morbidity and mortality associated with severe ITP in pregnancy.

DESIGN: A prospective national cohort study.

SETTING: UK.

POPULATION: Women with severe ITP, defined as platelets <50 × 109 /L in pregnancy or antenatal treatment of isolated low platelets.

METHODS: Data collected via the UK Obstetric Surveillance System (UKOSS) between 1 June 2013 and 31 January 2015 from all UK consultant-led obstetric units.

MAIN OUTCOME MEASURE: Incidence of severe ITP in pregnancy.

RESULTS: The estimated incidence of severe ITP in pregnancy is 0.83 per 10 000 maternities (95% CI 0.68-1.00). A total of 22 pregnant women (21%) did not receive any antenatal therapy, and 85 pregnant women (79%) received therapy. There was no difference between asymptomatic treated and untreated cohorts in severity of disease or outcome. Postpartum haemorrhage (51%) and severe postpartum haemorrhage (21%) was reported more frequently than the rate reported in the general pregnant population (5-10%). No neonates required treatment for thrombocytopenia and there were no cases of neonatal intracranial bleeding.

CONCLUSIONS: Current UK management of severe ITP in pregnancy results in an exceptionally low morbidity and mortality for the neonate. Mothers with ITP remain at increased risk of severe postpartum haemorrhage, and should be delivered at units that have the capacity to manage severe PPH effectively. Whilst balancing the risks for pregnancy from prophylactic antenatal treatment in asymptomatic women against observed low disease morbidity, we may be over treating asymptomatic patients.

TWEETABLE ABSTRACT: UKOSS study of severe ITP in pregnancy shows exceptionally low neonatal morbidity with current UK management.