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4. Temporal glucose profile measures and CGM use in pregnancy

      Maternal glucose, the major determinant of fetal growth and in predicting large for gestational age (LGA) infants and neonatal outcomes is dynamic, with glucose tolerance and insulin sensitivity varying across the whole day with the circadian rhythm. It is to this dynamic glucose signal that the fetus is exposed to during pregnancy. Continuous glucose monitoring (CGM) is the most objective method of assessing the dynamic glucose signal in the daily life of a pregnant woman with up to 288 interstitial fluid glucose measurements per day. Even though standard summary metrics are recommended for the reporting of CGM, they do not give dynamic information about the timing of glucose excursions and so losing much of the detailed temporal glycemic information generated.

      A research conducted by Scott et al on behalf of the CONCEPTT Collaborative group analyzed if there is a difference in the temporal glucose profiles between the three group of pregnant women: women who were randomized to RT-CGM or SMBG, women who used insulin pumps or MDIs, and women whose infants were born LGA or not, by assessing the CGM data obtained from the Continuous Glucose Monitoring in Women With Type 1 Diabetes in Pregnancy Trial (CONCEPTT). 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 is used to determine if temporal differences in 24-h glucose profiles occurred between comparators in each of the three groups. 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 (7-3 mg/dL) for 14 h/day at 34 weeks.

      The study concluded that FDA of temporal glucose profiles provide significant information about differences in glucose control and its timing, which are undetectable by standard summary metrics and women using RT-CGM were able to achieve better daytime glucose control, reducing fetal exposure to maternal glucose.

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