Primary hyperparathyroidism is a condition with hypercalcemia and elevated parathyroid hormone (PTH). Typically, treating patients with such disease does not pose a problem for doctors, unless the patient is pregnant. Firstly, pregnancy may mask signs of hypercalcemia. Secondly, treatment should be applied with special care for immature fetus. If undiagnosed and untreated, it is life-threatening for the mother and the baby. The main cause of primary hyperparathyroidism is parathyroid adenoma, which should be removed surgically in second trimester. If the patient is monitored by a multidisciplinary team, the risk of mortality and pregnancy loss is reduced.