OBJECTIVE: To describe the use of insulin pump therapy in women with gestational diabetes mellitus (GDM) or type 2 diabetes in pregnancy and persistent hyperglycemia despite multiple injections of subcutaneous insulin. RESEARCH DESIGN AND METHODS: As part of a service audit, deliveries to women with diabetes at a single South Auckland hospital were reviewed from 1991 through 1994. Glycemic control was estimated by the mean of self-recorded and laboratory postprandial glucose concentrations. In a nested case-control study, pregnancies complicated by GDM/type 2 diabetes with use of an insulin pump were compared with those without insulin pump therapy and peak insulin requirements of 100-199 units/ day, matched for ethnicity and type of diabetes. RESULTS: A total of 30 of 251 Polynesian, European, and South Asian women with singleton pregnancies complicated by insulin-requiring GDM/type 2 diabetes used an insulin pump. An additional two women with high insulin requirements discontinued pump therapy. None of the women with GDM/type 2 diabetes experienced severe hypoglycemia, whereas 79% of the women had improved glycemic control within 1-4 weeks. Mothers using a pump had greater insulin requirements (median maximum 246 vs. 130 units per day) and greater weight gain (10.6 vs. 5.0 kg). Their babies were more likely to be admitted to the Special Care Baby Unit but were neither significantly heavier nor experienced greater hypoglycemia than control subjects. CONCLUSIONS: Insulin pump therapy seems to be safe and effective for maintaining glycemic control in pregnancies complicated by GDM/type 2 diabetes and requiring large doses of insulin.