•ITP women do not increase their risk of severe bleeding during pregnancy.•NITP is associated with NITP history and the severity of maternal ITP during pregnancy. Display omitted The risk of immune thrombocytopenia (ITP) worsening during pregnancy and neonatal ITP (NITP) have never been prospectively studied. We included 180 pregnant and 168 nonpregnant women with ITP in a prospective, multicenter, observational cohort study. A total of 131 pregnant women with ITP were matched to 131 nonpregnant women with ITP by history of splenectomy, ITP status (no response, response, complete response), and duration. Groups were followed for 15 months. The primary outcome was the first occurrence of ITP worsening defined by a composite end point including bleeding events and/or severe thrombocytopenia (<30 × 109/L) and/or ITP treatment modification. We also studied the recurrence of ITP worsening and the incidence of NITP and risk factors. The first occurrence of ITP worsening did not differ between pregnant and nonpregnant women with ITP (53.4 per 100 person-years 95% confidence interval {CI}, 40.8-69.9 vs 37.1 95% CI, 27.5-50.0; hazard ratio {HR}, 1.35 95% CI, 0.89-2.03, P = .16). Pregnant women with ITP were more likely to have recurrence of severe thrombocytopenia and treatment modification (HR, 2.71 95% CI, 1.41-5.23, P = .003; HR, 2.01 95% CI, 1.14-3.57, P = .017, respectively). However, recurrence of severe bleeding events was not different between groups (P = .4). Nineteen (14%) neonates showed NITP <50 × 109/L. By multivariable analysis, NITP was associated with a previous offspring with NITP and maternal platelet count <50 × 109/L within 3 months before delivery (adjusted odds ratio, 5.55 95% CI, 1.72-17.89, P = .004 and 4.07 95% CI, 1.41-11.73, P = .009). To conclude, women with ITP do not increase their risk of severe bleeding during pregnancy. NITP is associated with NITP history and the severity of maternal ITP during pregnancy. These results will be useful for counseling women with ITP. There have been no prospective studies to establish the risk of pregnancy for patients with immune thrombocytopenia (ITP). In this Plenary Paper, Guillet and colleagues report on a prospective, multicenter observational cohort study comparing ITP outcomes in 131 pregnant vs 131 nonpregnant women with a history of ITP. Neonatal thrombocytopenia occurred in 14%, similar to previous reports. However, pregnancy did not increase bleeding or the degree of thrombocytopenia over nonpregnant patients, providing some reassurance to patients with ITP contemplating pregnancy.