OBJECTIVE: To investigate the effects of pregestational, as opposed to gestational, diabetes on infant malformations. METHODS: All women delivering infants at Parkland Hospital between January 1, 1991, and December 31, 2000, were ascertained. Screening for gestational diabetes was methodically employed throughout the study period using National Diabetes Data Group criteria for diagnosis of pregestational and gestational diabetes. Standardized definitions of major infant malformations were

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... ied before data analysis and subdivided according to the organ systems involved. RESULTS: A total of 145,196 women were delivered during the study period, and 2687 (1.9%) were diagnosed to have diabetes mellitus. Gestational diabetes was diagnosed in 2277 (1.6%) of whom 230 (10%) had fasting hyperglycemia diagnosed, and the remainder consistently demonstrated fasting serum levels less than 105 mg/dL. Pregestational diabetes was diagnosed in 410 (0.3%) women. Infant malformations occurred in 1.5% of nondiabetic women compared with 1.2% of women with normal fasting glucose gestational diabetes, 4.8% in women with gestational diabetes plus fasting hyperglycemia, and 6.1% in those with pregestational diabetes (P < .001, for comparison of the latter two groups with the nondiabetic population). CONCLUSION: Women with pregestational diabetes or gestational diabetes plus fasting hyperglycemia have a threeto four-fold increased risk of infant malformations, whereas women with mild gestational diabetes have malformation rates no different than the general nondiabetic obstetric population. (Obstet Gynecol 2002;100:925-30.