METHODS A 24-year-old pregnant woman had to be hospitalized in the 33rd week of pregnancy because of premature contractions and clinical signs of pyelonephritis. She had a history of nephrolithiasis. Laboratory tests showed a total calcium of 3.6 mmol/l, hypophosphataemia of 0.59 mmol/l and an increased parathormone level of 420 ng/l. Ultrasonography demonstrated a large parathyroid adenoma, confirming the diagnosis of primary hyperparathyroidism. RESULTS Despite several recommendations of conservative treatment in the literature it was decided to perform a parathyroidectomy, which was done without complication during the 35th week of pregnancy. A healthy, mature boy was born at the beginning ot the 41st week: at no time did he show any signs of hypoparathyroidism. CONCLUSIONS Surgical treatment of hyperparathyroidism is a reasonable and possible choice even in the 3rd trimester, because it allows regeneration of the fetal parathyroid. However, this decision must be individualized, in relation to the period of pregnancy and any progression of the disease.