Major hormonal changes emerge during pregnancy. The pituitary gland is one of the most affected organs with altered anatomy and physiology. The pituitary gland is enlarged as a result of lactotroph hyperplasia. Due to physiological changes in the pituitary and target hormone levels, binding globulins, and placental hormones, hormonal evaluation becomes more complex in pregnant women. As a consequence of physiological hormonal changes, the evaluation of pituitary functions in pregnant women is quite different from that done in the prepregnant state. Pituitary adenomas may cause problems by their hormone secretion that affects the mother and the fetus besides causing an increased risk of tumor growth. Furthermore, diagnosis, course, and treatment of pituitary diseases point out differences. The changes in anatomy and physiology of the pituitary gland during pregnancy are reviewed. Pituitary disorders namely Cushing's disease; acromegaly; prolactinoma; TSH-secreting, gonadotropin-producing, and clinically nonfunctioning adenomas; craniopharyngioma; and Sheehan's syndrome, which is one of the most common causes of hypopituitarism, lymphocytic hypophysitis, and hypopituitarism, in relation to pregnancy are discussed. Being aware of all this information will prevent any serious problems which mother and child will be exposed to.