Macroprolactinomas have a well-recognized potential for marked expansion during pregnancy. Measures advocated to minimize this risk include prior treatment with dopamine agonists, radiotherapy and pituitary surgery. We describe a patient who underwent transsphenoidal surgery with the removal of an histologically proven prolactin-secreting adenoma with the intention of rendering subsequent pregnancy safe. The patient remained hyperprolactinaemic and received prolonged therapy with metergoline and bromocriptine which suppressed prolactin to normal and she conceived after induction of ovulation with human menopausal gonadotrophin and human chorionic gonadotrophin. At 3 months gestation she developed headaches, vomiting, reduced visual acuity and bitemporal hemianopia caused by massive pituitary expansion. Reintroduction of bromocriptine rapidly abolished features of tumour expansion and after delivery of a full-term normal female infant, repeat CT scan documented tumour shrinkage.