Information on the course and outcome of pregnancies in growth hormone (GH)-deficient patients is sparse, and GH treatment during pregnancy in such women has not been described previously. We have studied fetal growth and serum levels of GH, insulin-like growth factor I (IGF-I) and IGF binding protein 3 (IGFBP-3) during pregnancy, as well as birth weight and hormone levels after delivery in a 25-year-old woman with idiopathic, isolated GH deficiency diagnosed at the age of 7 years. As part of a clinical trial, the patient was treated with 2 IU/M2 GH for a period of 5 years. At this time she became pregnant after donor insemination. The GH treatment was continued until variant GH production from the placenta was evident. Serum levels of GH, IGF-I and IGFBP-3 were measured monthly during pregnancy after 3 days off GH therapy. Abdominal ultrasound was performed five times. Hormonal levels were measured immediately after delivery and during the following days. Serum GH and IGF-I levels increased during the second half of pregnancy; serum IGFBP-3 remained constant throughout pregnancy at a normal level. Serum levels of GH fell within 1 h after delivery, and levels of IGF-I and IGFBP-3 decreased into the range of GH-deficient women 4 days after. The fetal biparietal diameter increased normally, and birthweight was 3.564 kg, length 52 cm. No adverse events were recorded. We conclude that the role of GH replacement during pregnancy of GH-deficient women should be investigated further.