To date, little is known about the fertility of women suffering from mucopolysaccharidosis type I (MPS I). We report on a female patient with MPS I treated by allogeneic bone marrow transplantation (BMT) at the age of 4 years (after a conditioning regimen containing busulfan 16 mg/kg and cyclophosphamide 100 mg/kg) who had four successful pregnancies without any reproductive assistance. Clinical and biological examinations of the children were normal. On the basis of this case, we discuss the fertility counselling of female MPS I patients at the time of BMT.