JAK2 and myeloproliferative neoplasm: The calreticulin (CALR) gene is the second most common driver mutation in MPN and is associated with a lower risk of thrombosis than the JAK2 mutation.53,54 Because most studies have reported on pregnancies before the 2013 discovery of the CALR mutation, whether pregnancy differs in CALR-mutated MPNs is unknown and needs further exploration.