Abstract: Background: Primary myelofibrosis (PMF) is an incurable myeloproliferative disease that affects mainly elderly men and women. Very rarely, PMF may occur in fertile women. In case of an associated pregnancy the disease in itself and the necessary treatment may result in an increased risk for the mother and the fetus. Case: The patient, who was diagnosed with an infantile PMF at age 21, had hepatosplenomegaly since early childhood. She became pregnant at age 35 and had an unexpectedly uneventful pregnancy and spontaneous delivery at term. Conclusion: Despite of the risks reported in literature the interdisciplinary hematological and obstetrical care with close monitoring made a successful pregnancy possible. To our knowledge this is the first report of a successful gestation in a patient with infantile PMF. The uneventful course of this gestation is in contrast to the published risk of complications during pregnancy and delivery in patients with adult PMF.