Non-glycemic-dependent reduction of late pregnancy A1C levels in women with type 1 diabetes.

A reduction of A1C levels during pregnancy in women without diabetes has been reported (1–6), suggesting that the goal for A1C during pregnancy complicated with diabetes should be lowered. The decrease in fasting blood glucose levels during the first trimester of normal pregnancy (7,8) may explain the lower A1C levels found in early pregnancy (1,2,3,5). A further decrease of A1C in late pregnancy in women without diabetes has been reported by Nielsen et al. (3), which may be related to decreased erythrocyte life span (9,10). In women with type 1 diabetes, strict glycemic control during pregnancy leads to a reduction in A1C levels, which may be insufficient to prevent the complications of pregnancy in type 1 diabetes (11,12). Since the decrease in A1C during normal pregnancy is related to lower blood glucose and to decreased erythrocyte lifespan (6 –10), some of the reduction of A1C observed in pregnant women with type 1 diabetes will not be related to improved glycemic control. Therefore, A1C levels in pregnancies complicated by diabetes can be misleading when evaluating the degree of glycemic control. The aim of this study was to quantify the decrease in A1C levels during late pregnancy in women with type 1 diabetes who were not dependent on glycemic control.