Comparison of the results of blood glucose self-monitoring and continuous glucose monitoring in pregnant women with previous diabetes mellitus

Abstract

Background: Pregnancy is one of the indications for continuous glucose monitoring (CGM). The data on its efficiency in pregnant women are contradictory. Aim: To compare the results of blood glucose self-monitoring (SMBG) and CGM in pregnant women with previous diabetes mellitus. Materials and methods: We performed a cross-sectional comparative study of glycemia in 18 pregnant women with previous type 1 (87.8% of patients) and type 2 diabetes (22.2% of patients) with various degrees of glycemic control. Their age was 27.7 ± 4.9 year. At study entry, the patients were at 17.2 ± 6.1 weeks of gestation. CGM and SMBG were performed in and by all patients for the duration of 5.4 ± 1.5 days. Depending on their hba1c levels, all patients were divided into two groups: group 1 – 12 women with the hba1c above the target (8.5 ± 1%), and group 2 – 6 women with the hba1c levels within the target (5.6 ± 0.3%). Results: According to SMBG results, women from group 2 had above-the-target glycemia levels before breakfast, at 1 hour after breakfast and at bedtime: 6.2 ± 1.6, 8.7 ± 2.1, and 5.7 ± 1.9 mmol/L, respectively. According to CGM, patients from group 1 had higher postprandial glycemia than those from group 2 (8.0 ± 2.1 and 6.9 ± 1.8 mmol/L, respectively, p = 0.03). The analysis of glycemia during the day time revealed significant difference between the groups only at 1 hour after dinner (7.1 ± 1.4 mmol/L in group 1 and 5.8 ± 0.9 mmol/L in group 2, р = 0.041) and the difference was close to significant before lunch (6.0 ± 2.2 mmol/L in group 1 and 4.8 ± 1.0 mmol/L in group 2, р = 0.053). Comparison of SMBG and CGM results demonstrated significant difference only at one timepoint (at 1 hour after lunch) and only in group 1: median glycemia was 7.4 [6.9; 8.1] mmol/L by SMBG and 6 [5.4; 6.6] mmol/L by CGM measurement (р = 0.001). Lower median values by CGM measurement could be explained by averaging of three successive measurements carried out in the period of rapid changes of glycemia. Conclusion: The achievement of control of diabetes by hba1c doesn't necessarily reflect current achievement of the target glycemic levels. As long as there was no significant difference in glycemia measured by SMBG and CGM, we conclude that CGM doesn't have any advantage over routine frequent SMBG in pregnant women.