[Struma ovarii during pregnancy]. / Struma ovarii tijdens de zwangerschap.

A 41-year-old pregnant woman, gravida 10, para 7, with gestational diabetes, was diagnosed with subclinical hyperthyroidism. At 16-weeks gestation a left-sided unilateral ovarian cyst was discovered. At 37 weeks of pregnancy an elective caesarean section was carried out, due to the transverse presentation caused by the cyst, followed by an adnexectomy. Histological examination showed a struma ovarii, a rare mature ovarian teratoma mainly consisting of thyroid tissue. There was no evidence of malignancy.