Continuous Glucose Monitoring in Pregnancy: Importance of Analyzing Temporal Profiles to Understand Clinical Outcomes

Abstract

Objective: To determine if temporal glucose profiles differed between 1) women who were randomized to real-time continuous glucose monitoring (RT-CGM) or self-monitored blood glucose (SMBG), 2) women who used insulin pumps or multiple daily insulin injections (MDIs), and 3) women whose infants were born large for gestational age (LGA) or not, by assessing CGM data obtained from the Continuous Glucose Monitoring in Women With Type 1 Diabetes in Pregnancy Trial (CONCEPTT).

Research design and methods: Standard summary metrics and functional data analysis (FDA) were applied to CGM data from the CONCEPTT trial (RT-CGM, n = 100; SMBG, n = 100) taken at baseline and at 24- and 34-weeks' gestation. Multivariable regression analysis determined if temporal differences in 24-h glucose profiles occurred between comparators in each of the three groups.

Results: FDA revealed that women using RT-CGM had significantly lower glucose (0.4-0.8 mmol/L [7-14 mg/dL]) for 7 h/day (0800 h to 1200 h and 1600 h to 1900 h) compared with those with SMBG. Women using pumps had significantly higher glucose (0.4-0.9 mmol/L [7-16 mg/dL]) for 12 h/day (0300 h to 0600 h, 1300 h to 1800 h, and 2030 h to 0030 h) at 24 weeks with no difference at 34 weeks compared with MDI. Women who had an LGA infant ran a significantly higher glucose by 0.4-0.7 mmol/L (7-13 mg/dL) for 4.5 h/day at baseline, by 0.4-0.9 mmol/L (7-16 mg/dL) for 16 h/day at 24 weeks, and by 0.4-0.7 mmol/L (7-13 mg/dL) for 14 h/day at 34 weeks.

Conclusions: FDA of temporal glucose profiles gives important information about differences in glucose control and its timing, which are undetectable by standard summary metrics. Women using RT-CGM were able to achieve better daytime glucose control, reducing fetal exposure to maternal glucose.

Figure 1

Differences in mean temporal glucose levels across the 24-h day, assessed by FDA (at 24 and 34 weeks’ gestation combined) between those women who were randomized to RT-CGM (represented by the dark wavy line) compared with those using SMBG (represented by the horizontal zero dotted line) with 95% pointwise CIs (gray section). Where both of the CIs sit to the same side of 0.0, there is a significant difference. Dashed vertical lines represent daytime at 0700 h and 2300 h. *Significant differences using 95% CIs.

Figure 2

Differences in mean temporal glucose levels across the 24-h day, assessed by FDA. A: Differences in women who used pumps (represented by dark wavy line) compared with those on MDI (represented by the horizontal zero dotted line) with 95% pointwise CIs (gray section). B: Differences in women who gave birth to an LGA infant (represented by the dark wavy line) compared with those who did not (represented by the horizontal zero dotted line) with 95% pointwise CIs (gray section). Dashed vertical lines represent daytime at 0700 h and 2300 h. *Significant differences using 95% CIs.