A 33-year-old primagravida with a history of polycystic ovary syndrome was referred because of symptoms of moderate hyperandrogenism. Serum hormone levels, measured regularly from the 7th week of pregnancy until delivery, showed very high increases of testosterone, androstenedione and estradiol. Ultrasound showed no evidence of adrenal or ovarian masses. She delivered a female newborn with normal female external genitalia. Umbilical cord hormone levels were normal, except for a modest increase of serum testosterone. After delivery the androgen levels of the mother returned to normal and the symptoms of hyperandrogenism were also slightly improved.