Basal Hyperglycemia Contributes More Than 50% to Time in Range in Pregnant Women With Type 1 Diabetes

Objectives:To evaluate the relative contribution of basal hyperglycemia (BHG) and postprandial hyperglycemia (PHG) to the time in range (TIR) categories and adverse pregnancy outcomes in pregnant women with type 1 diabetes mellitus (T1DM). Materials and Methods: This observational study included 112 pregnancies with T1DM from the CARNATION study who wore continuous glucose monitoring (CGM) devices during pregnancy. The data from CGM were analyzed for TIR (range, 3.5-7.8 mmol/L), areas under the curve of PHG, area under the curve of BHG, and BHG and PHG contribution rates. The contribution rates of BHG and PHG to the different levels of TIR (<60%, 60-78%, >= 78%) and adverse pregnancy outcomes were analyzed. Results: The participants' average age was 28.8 +/- 3.9 years with a diabetes duration of 8.4 +/- 6.2 years. All women experienced a mean TIR of 75.6 +/- 19.0% and a mean glycated hemoglobin of 6.2 +/- 1.1% during pregnancy. The BHG contribution accounted for 74.9% (36.8, 100), 69.2% (13.4, 100), and 66.5% (10.0, 100) (P < .001) and PHG accounted for 25.1% (0, 63.2), 30.8% (0, 86.6), and 33.5% (0, 90.0) (P < .001) when participants experienced the TIR<60%, 60%-78%, and >= 78%, respectively. Participants with higher BHG contribution rates tended to have more adverse pregnancy outcomes. Conclusion: Basal hyperglycemia was the major contributor to TIR during pregnancy. Along with controlling PHG, pregnant women with T1DM who did not reach the target of TIR may benefit more from the optimization of insulin regimens focusing on reducing basal glucose.