A 29 year old woman, 21 weeks pregnant with no previous medical history was admitted with 5 days blurred vision in the left eye and headaches, worse in the morning and lying flat. Three weeks previously she had been treated with antibiotics for a group A strep infection. An urgent MRI suggested pituitary apoplexy with left optic chiasm nerve compression. IV hydrocortisone 100 mg TDS was commenced reduced to 20 mg TDS. Investigations showed TSH 0.2 mu/l, FT4 10.4 pmol/l, FT3 2.6 pmol/l. Prolactin concentration was normal for pregnancy. Thyroxine 50 mcg/day was commenced. Subsequently she developed mild diabetes insipidus (DI) managed with oral desmopressin (DDAVP). In view of progressive deterioration of her visual fields, urgent transphenoidal decompression of the chiasm was performed. Following surgery vision improved substantially, but DI persisted, requiring high doses of DDAVP. Histology suggested the most likely diagnosis was autoimmune lymphocytic hypophysitis. Follow up was in the interdisciplinary maternal medicine clinic with monitoring of electrolytes. She was induced at 38 weeks. Fluid balance, serum electrolytes and urine osmolality were monitored closely during labour and delivery, the DDAVP doses adjusted as indicated. A healthy baby was delivered. Post-delivery short synacthen test was normal and oral hydrocortisone stopped. DI also resolved four months postpartum and DDAVP was discontinued. Currently she remains on thyroxine. Throughout this stressful experience the patient was supported by the Pituitary Nurse Specialist for advice, guidance and psychological support. This report describes the unusual occurrence of pituitary apoplexy complicated by DI occurring during pregnancy, and its successful management throughout remaining pregnancy and labour. Lymphocytic hypophysitis is a rare condition where the pituitary gland is infiltrated by lymphocytes, with pituitary enlargement and impaired function. It often occurs in women in late pregnancy or the postpartum period. The exact cause is unknown, but maybe autoimmune related.