De Novo ITP Diagnosed during Pregnancy : Outcome for the Mothers and the Neonates and Prospective Comparative Study with Chronic ITP Pregnant Women

Background and Objective : Outcome, severity and transition to chronic illness of de novo ITP diagnosed during pregnancy and incidence of neonatal ITP (NITP) in this subset of patients have never been prospectively described. We conducted a prospective multicentric study in France to evaluate the outcome of patients with ITP during pregnancy (Clinical Trials.gov ID NCT02892630). One of the aims of this study was to investigate the evolution of ITP in patients with known ITP prior to pregnancy (« chronic group »). The results of this first part of the study have been recently published (Guillet et al, Blood ; 141 :11-21). Another aim was also to prospectively study the outcome of patients with ITP appeared and diagnosed during pregnancy (“ de novo group”) and to compare them with the previous group. We report the results here.

Methods:De novo ITP was defined by a normal platelet count before pregnancy and a nadir < 50x10 ⁹/L during pregnancy without any other clinical or biological abnormalities in particular no sign of pregnancy-specific causes of thrombocytopenia. We used a stringent platelet count threshold <50x10 ⁹/L to avoid misdiagnosis with gestational thrombocytopenia. Patients were followed during pregnancy and 6 months after delivery. We compared ITP outcome in both groups (“ chronic” and “ de novo” groups) including episodes of bleeding events, severe thrombocytopenia (<30x10 ⁹/L) and ITP treatment modification. We also studied obstetrical complications and NITP incidences in both groups.

Results: 34 “ de novo” ITP women diagnosed during pregnancy were included and compared with 61 chronic ITP pregnant women. De novo ITP was diagnosed equally during the first, second and third trimester, in respectively 29.4% (10/34), 32.4% (11/34) and 38.2% (13/34). Among these 34 women, 29.4% (10/34) were primiparous. De novo ITP pregnant women experienced during follow-up, severe thrombocytopenia in 50% [35.5-91.9], bleeding events in 41.2% [26.8-59.4] including 11.8% [4.6%-28.4%] severe bleeding events with a French bleeding score > 8 and ITP therapeutic interventions in 76.5% [61.4-88.9]. Episodes of severe thrombocytopenia and bleeding events including severe bleeding event were similarly observed in “ de novo” and “ chronic” groups (data not shown). However, chronic ITP pregnant women underwent less ITP therapeutic interventions 50.8% [39.1-63.8], p=0.039. Obstetrical complications including preterm delivery, postpartum hemorrhage and cesarean delivery rates were similar in both groups (data not shown). NITP <50x10 ⁹/L was observed in 6/31 (19.3%) neonates of women with de novo ITP and was similar to those observed in neonates of chronic ITP women 9/53 (17%). With a median follow-up of 6 months [5-7] after delivery, de novo ITP remained active for 25/34 women (73.5%).

Conclusion: The severity of de novo ITP diagnosed during pregnancy and the risk of NITP are closely similar to those observed in chronic ITP pregnant women. Non-fatal severe bleeding events occur in around 10% of patients. De novo ITP remains active 6 months after delivery in a large majority of patients. Our study is still in progress to better assess the risk of chronic evolution (more than one year of duration) of de novo ITP after delivery.