A unique case of fetal goiter accompanied by bilateral ovarian cysts in a mother treated with methimazole for Graves' disease is reported. The abnormal findings were detected by ultrasound at 31 weeks of gestation. Umbilical fetal blood sampling revealed elevated serum TSH, normal concentrations of free T 4, normal FSH and LH and high concentrations of E 2. A series of weekly amniocenteses and intra-amniotic injections of levothyroxine was initiated, along with a reduction of the mother's methimazole dosage. The level of TSH in amniotic fluid was initially high, but was considerably reduced by each injection and followed by a gradual reduction of fetal goiter as well as the left ovarian cyst. The right cyst ruptured spontaneously. At 36 weeks + 4 days, the patient underwent elective caesarean section and gave birth to a female, weighing 2,880 g with 1- and 5-min Apgar scores of 10. The thyroid gland appeared normal in size, and cord blood TSH and free T 4 were both within normal limits. At ultrasound control 6 days later, the right ovarian cyst was not visible, while the left cyst was still present. Thus, our report supports previous findings that fetal goiter can be treated successfully with intra-amniotic injection of levothyroxine. More importantly, it shows that fetal hypothyroidism with elevated levels of TSH can be accompanied by ovarian cysts, suggesting interference between thyreotropic and gonadotropic hormones.