Do HbA1c levels and the self-monitoring of blood glucose levels adequately reflect glycaemic control during pregnancy in women with type 1 diabetes mellitus?

Aims/hypothesis: Pregnancies of women with type 1 diabetes mellitus are associated with maternal and perinatal complications. These complication rates remain elevated despite achievement of the treatment goals described in the widely used guidelines of the American Diabetes Association (i.e. HbA(1)c level >= 7.0%). Against this background, we sought to answer two questions: (1) are HbA(1)c levels within 1% above normal appropriate in pregnant women with type 1 diabetes or should treatment be aimed at normal HbA(1)c levels; and (2) how many self-monitored blood glucose (SMBG) levels are needed per day to obtain an adequate image of glycaemic control in pregnant women with type 1 diabetes? Materials and methods: We asked 43 pregnant women with type 1 diabetes to use the Continuous Glucose Monitoring System (CGMS) once in each trimester of pregnancy, while continuing their SMBG measurements. Glucose levels measured with the CGMS were compared between patients with HbA(1)c levels of 4.0-6.0%, 6.0-7.0% and > 7.0%. Self-monitored glucose levels and those measured with CGMS were compared between patients with four or five, six to nine and ten or more SMBG determinations daily. Results: In patients with HbA(1)c levels >= 6.0%, the glucose levels obtained by CGMS were significantly better than in patients with HbA(1)c levels > 6.0%. In women with HbA(1)c levels 6.0-7.0% and > 7.0%, these levels did not differ. The detection rate of hyper- and hypoglycaemic episodes was significantly higher in patients with ten or more SMBG determinations daily than in patients with fewer than ten. Conclusions/interpretation: Treatment of diabetes in pregnant women should be aimed at achieving HbA(1)c levels within the normal range, i.e. >= 6.0%. A minimum of ten SMBG determinations daily is necessary to obtain adequate information of all daily glucose fluctuations.