An increased risk of pregnancy complications was recently reported in JAK2V617F-positive essential thrombocythemia (ET). In the current study of 63 pregnancies among 36 women with ET, we sought to appraise this association and identify other predictors of outcome. Overall outcome included 38 (60%) births and 20 (35%) first trimester spontaneous abortions. Among 36 first pregnancies, 22 (61%) resulted in live birth. Twelve of the 14 pregnancy losses occurred during the first trimester. Rate of pregnancy loss was 21% among 24 patients receiving aspirin therapy during the first trimester vs. 75% among 12 patients not receiving such treatment (P = 0.002). Pregnancy outcome was not influenced by platelet count, leukocyte count or presence of JAK2V617F; four pregnancy losses each were documented in 10 mutated and 10 unmutated patients. Among 17 second pregnancies, 12 (71%) resulted in live birth; these included eight from nine patients with successful and four from eight with unsuccessful first pregnancies (P = 0.07). Maternal complications were infrequent (11%): pre-eclampsia (n = 1), hematoma after Cesarean-section (n = 2) and post-partum hemorrhage (n = 1). This study suggests a salutary role for aspirin therapy in pregnant women with ET. Furthermore, the occurrence of a miscarriage in ET might be a marker for a similar event during subsequent pregnancies.
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