Poor glucose control in women with type 1 diabetes mellitus and 'safe' hemoglobin A1c values in the first trimester of pregnancy.

To observe glycemic excursions, measured continuously over 24 h, in relation to hemoglobin A1c values in the first trimester of pregnancy of women with type 1 diabetes mellitus. The MiniMed Continuous Glucose Monitoring System (CGMS) was used to obtain glucose values every 5 min during 24 h. Hemoglobin A1c was determined at the end of the continuous glucose recording and 6-12 weeks after the continuous glucose recording. Continuous glucose recordings were obtained in 13 women between 7 and 15 weeks of gestation. Nine patients had hemoglobin A1c levels of < or = 7.0% (< 1% above the upper limit of normal range) while up to 41.3% of the readings had values of < 3.9 mmol/l (70 mg/dl) and up to 52.8% of the readings had values of > 7.8 mmol/l (140 mg/dl). Hemoglobin A1c does not reflect the complexities of glycemic control in women with type 1 diabetes who are considered to have accomplished tight glycemic control in the first trimester of pregnancy.