Mrs T is a 40-year-old woman with type 2 diabetes and chronic hypertension who has had a gastric bypass procedure and is planning to conceive. She would like to know whether she can continue using metformin during the pregnancy and also is concerned about the effect of the gastric bypass surgery. This article discusses the management of diabetes prior to and during pregnancy, including appropriate preconception evaluation and the use of insulin and oral antidiabetic agents. The implications of gastric bypass surgery for pregnancy are also outlined. Important aspects include the need to optimize metabolic control prior to conception, to evaluate and treat vascular complications of diabetes prior to conception, and to provide the services of a health care team to gravid women with diabetes. Gastric bypass surgery with subsequent weight loss is likely to ameliorate type 2 diabetes, and special attention must be paid to nutrition when women who have undergone such procedures become pregnant.