Gestational diabetes

CGM gives better profile of nocturnal glycaemic excursions in GDM

CGM provides a more comprehensive assessment of nocturnal hyperglycemia than self-monitoring of blood glucose (SMBG) in women with gestational diabetes, Australian clinicians say.

A Victorian study of 90 women with newly diagnosed gestational diabetes at 24-28 weeks compared the SMBG data used to guide clinical interventions with seven days of CGM data.

Most women (62%) were managed with diet and lifestyle measures while the rest of the women (38%) required insulin.

The study by Dr Bala Krishnamurthy and colleagues at the University of Melbourne, found 61% of the women on diet and lifestyle measures breached the nocturnal glycaemic targets for more than 10% of the time. Further, 20% of the women also breached the daytime targets.

The majority of exposure to hyperglycemia occurred in the early morning between midnight and 3 am.

“The SMBG measurement following the evening meal usually occurred between 7pm and 10pm and this blood-glucose measurement at a single time-point would have provided only a limited insight into overnight hyperglycemia as would the pre-breakfast reading,” the study authors said.

While the incidence of large for gestational age (LGA) infants was a low 8% overall, the authors noted that five of the seven women with LGA babies were not commenced on insulin and three of those women had breached nocturnal glycemic thresholds.

There were no premature deliveries or neonatal deaths.

While the study was not powered to definitively explore the relationship between CMG and LGA, the authors said other studies have demonstrated improved neonatal outcomes with the use of CGM in gestational diabetes and type 1 diabetes.

“Our data suggest that the majority of nocturnal hyperglycemia occurs during the first half of the night implying delayed clearance of the evening meal as the major underlying mechanism rather than the diurnal variation in cortisol levels,” the study authors said.

“The impact of bedtime intermediate acting insulin vs. long acting insulin analogues on nocturnal hyperglycaemia in CGM would be worth testing in a future study.”

The findings are published in Diabetes Technology and Therapeutics.

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