Interferon alpha for essential thrombocythemia during 34 high-risk pregnancies: outcome and safety

Pregnancies in women with essential thrombocythemia (ET) are at a higher risk for obstetrical complications. Acetylsalicylic acid (ASA) and low-molecular weight heparin (LMWH) are common options to prevent miscarriages and maternal complications, whereas interferon alpha (IFN) seems to be the cytoreductive therapy of choice. This retrospective study analyzes the largest number of IFN pregnancies to date in terms of outcome and safety. Data of 34 high-risk pregnancies in 23 women presenting at the University hospitals of Minden and Jena from 01-Jun-2007 to 01-Jun-2020 were collected. Reasons defining high-risk ET pregnancy in all 23 patients were: Thrombosis (n = 9) or severe hemorrhage (n = 2) in history, platelet count ≥ 1500 × 103/µl (n = 8) or severe microcirculatory disturbances not completely responding to ASA (n = 4). Without the use of IFN, live birth rate was 60% (6/10), however, after the use of IFN live birth rate increased to 73.5% (25/34 pregnancies). Nine pregnancies ended in miscarriages (9/34; 26.5%); all of them spontaneous abortions. Live birth rate significantly improved with ASA (90% versus 50%, p = 0.0168), however, if ASA and LMWH was added (n = 14), live birth rate was 100%. IFN compound (PEGylated versus standard IFN) and JAK2-driver mutation had no impact on pregnancy outcome. One major maternal complication occurred as a major peripartal bleeding after abortion curettage. IFN was associated with an encouraging live birth rate of 73.5% with no fatal maternal events and manageable side effects.