Objectives: To investigate the frequency of severe hypoglycemia (SH) and hypoglycemic coma during the first trimester of type 1 diabetic pregnancy and in the 4 months before gestation and to identify risk indicators predicting first trimester SH in a nonselected nationwide cohort of pregnant women with type 1 diabetes.
Research design and methods: We conducted a longitudinal cohort survey in 278 pregnant type 1 diabetic women using questionnaires at inclusion and at 17 weeks of gestation, addressing the frequencies of SH (i.e., external help required) and hypoglycemic coma, general characteristics, hypoglycemia awareness, blood glucose symptom threshold, and the Hypoglycemia Fear Survey.
Results: The occurrence of SH (including hypoglycemic coma) rose from 0.9 +/- 2.4 episodes per 4 months before gestation to 2.6 +/- 6.3 episodes during the first trimester (P < 0.001), including an increase in episodes of coma from 0.3 +/- 1.3 to 0.7 +/- 3.7 (P=0.03). The proportion of women affected by SH rose from 25 to 41% (P < 0.001). First-trimester SH was independently related to a history of SH before gestation (odds ratio [95%CI]: 9.2 [3.9-21.7]), a 10 years' longer diabetes duration (1.6 [1.0-2.4]), an HbA1c level < or = 6.5% (2.5 [1.3-5.0]), and a 0.1 unit/kg higher daily insulin dose (5.4 [1.5-18.9]), adjusted for a decreased symptom threshold.
Conclusions: In type 1 diabetic pregnancy, the risk of SH is increased already before pregnancy and rises further during the first trimester. A history of SH before gestation, longer duration of diabetes, an HbA1c level < or = 6.5%, and a higher total daily insulin dose were risk indicators predictive for SH during the first trimester. Further research should aim to elucidate how the benefits of strict glycemic control balance with the markedly increased risk of SH early in pregnancy.