CALCA and essential thrombocythemia: Data regarding the association between Philadelphia-negative chronic myeloproliferative neoplasms and pregnancy mainly pertain to essential thrombocythemia and suggest substantial maternal morbidity, including preeclampsia/eclampsia, intrauterine growth restriction, stillbirth, and premature delivery.29 These disorders are associated with acquired variations in the Janus kinase 2 (JAK2), calcitonin (CALC), or MPL protooncogene, thrombopoietin receptor (MPL) genes, which have not been described in those with preeclampsia/eclampsia.