Adult growth hormone deficiency (AGHD) is a recently recognized endocrine disorder characterized by low peak GH levels during provocative tests. The AGHD has a negative impact on bone mineral density, skeletal muscle strength, physical capacity and psychosocial well-being. Furthermore, the girls with GHD have delayed pubertal development, and in adulthood present a condition of subfertility. Treatment for AGHD with GH replacement therapy has been officially approved since 2006 in Japan. The patient was diagnosed as pituitary dwarfism at age 9. She was treated with GH replacement therapy since diagnosis until her height reached 155cm at age 15. When she was 24 years old, she suffered from clinical symptoms relating to GH deficiency, and she visited our hospital for reintroduction of the therapy to alleviate these clinical symptoms. She has been treated with the replacement therapy since then. The patient’s dysmenorrhea improved. And she was found to be 8 weeks pregnant at age 28 years 7 months. We immediately ceased replacement therapy and carefully observed the patient, because it is not indicated for female patient with pregnancy. She delivered a healthy girl at 40 weeks of pregnancy, no recognizable side-effects were observed in either mother or baby. To our knowledge, there are no other reports of a Japanese patient becoming pregnant during GH replacement therapy, and few cases have been reported in other countries. It remains uncertain whether the therapy is safe and essential for fetal development, fertility, and continuation of pregnancy in AGHD subjects.