Primary Hyperparathyroidism (pHPT) affects approximately 1:2000 women under 40 years of age, so pHPT in pregnancy is uncommon. It is associated with significantly increased risks of morbidity for mother and foetus. Conventionally, surgery is recommended, ideally early in the second trimester. A 31-year-old woman attended the Accident and Emergency department at 26+4 weeks of her third gestation, with severe loin pain and fever. She had a past medical history of pyelonephritis. Of note, her father had previously undergone parathyroidectomy for a parathyroid adenoma. On admission, the adjusted calcium level was found to be 2.94 mmol/l, phosphate level 0.35 mmol/l, PTH level 18.4 pmol/l, with hypercalciuria of 6.3 mmol/24hrs and evidence of acute kidney injury. A renal ultrasound scan revealed a left ureteric calculus measuring 1 cm, causing moderate left-sided hydronephrosis. A left nephrostomy stent was inserted relieving the obstruction. Serum calcitonin and fasting gut hormone levels were normal. Genetic testing for Multiple Endocrine Neoplasia is underway. With aggressive intravenous rehydration, the adjusted calcium level normalised to 2.49 mmol/l, but rose again to 2.76 mmol/l. In the context of the evidenced end-organ damage due to hypercalcaemia, a decision was made to perform parathyroidectomy at 30+3 weeks of gestation. Pre-operative intravenous steroids were administered, to minimise foetal risk. Ultrasound scan of the neck revealed two suspected parathyroid adenomas. At surgery, 3 parathyroid glands were removed and the intraoperative PTH level decreased from 70 to 7 pmol/l. Post-operatively, the adjusted calcium level was 2.17 mmol/l initially and 2.29 mmol/l subsequently. The procedure was uneventful. Parathyroidectomy in pregnancy needs to be carefully planned and discussed with an expert multidisciplinary team, particularly with regards to optimal perioperative care and timing, in order to minimise risk to mother and foetus, including miscarriages, pre-eclampsia and neonatal tetany.