A cutoff of the time above the target range (TAR) for continuous glucose monitoring (CGM) of 10% or greater in individuals being screened for gestational diabetes mellitus (GDM) is associated with an increased risk of adverse outcomes, according to a recent study published in the American Journal of Obstetrics & Gynecology.
Takeaways
- A cutoff of 10% or greater in the time above the target range (TAR) for continuous glucose monitoring (CGM) during screening for gestational diabetes mellitus (GDM) is associated with an increased risk of adverse neonatal outcomes.
- Over 1000 cases of GDM are diagnosed daily in the United States, leading to adverse outcomes such as hypertensive disorders, cesarean delivery, large for gestational age (LGA) babies, shoulder dystocia, neonatal intensive care unit admissions, hypoglycemia, and birth injuries.
- GDM is commonly diagnosed in the U.S. through a 1-hour glucose challenge test (GCT), which is followed by a 3-hour GCT if the result is abnormal. However, this approach has limitations and may delay treatment actions aimed at preventing adverse pregnancy and birth outcomes.
- A prospective observational study involving CGM was conducted to identify the glycemic profile during GCT in individuals being screened for GDM. The study included participants who received a 50-g GCT, with a CGM device attached for up to 10 days.
- Participants with a TAR of 10% or more had a 63% risk of adverse neonatal outcomes, compared to 19% in those with a TAR under 10%.
Over 1000 cases of GDM are diagnosed in the United States per day, with associated adverse outcomes including hypertensive disorders of pregnancy, cesarean delivery, large for gestational age (LGA), shoulder dystocia, neonatal intensive care unit admission, hypoglycemia, and birth injuries. The risks of these outcomes can be reduced through diagnosis and prevention methods.
In the United States, GDM is commonly diagnosed through a 1-hour glucose challenge test (GCT), followed by a 3-hour GCT if the result is abnormal. However, this method contains limitations, such as not being focused on preventing adverse pregnancy and birth outcomes and the length delaying treatment actions.
To identify the glycemic profile at GCT using GDM, investigators conducted a prospective observational study. Participants were aged over 18 years and received obstetrical care at 30 weeks of gestation or less at a single level IV center from June 2020 to January 2022, during which they were screened for GDM.
Exclusion criteria included known type 1 or type 2 diabetes mellitus, allergy to adhesive materials, and history of bariatric surgery. All participants received a 50-g GCT, with plasma collection occurring 60 minutes after the GCT. During the 50-g GCT, participants received a blinded CGM device for up to 10 days.
The CGM device included a sensor, applicator, and serial identifications. Participants continued their usual meal and life habits during monitoring. Every 5 minutes, the device measured patients’ interstitial glucose. Participants were asked to remove the sensor by a message sent to them after 10 days.
A glucose level of 135 mg/dL was considered abnormal. A glucometer was used to measure blood glucose levels 4 times a day. GDM was managed through recommended goals, including fasting of 95 mg/dL or less, 150 mg/dL or less 1 hour after a meal, and 120 mg/dL or less 2 hours after eating a meal.
Composite adverse neonatal outcomes were measured as the primary outcome of the analysis, including LGA, respiratory distress, shoulder dystocia, need for intravenous (IV) glucose therapy, and fetal or neonatal death. Data collected included maternal demographic, antepartum, labor course, and neonatal outcomes.
There were 92 individuals included in the final analysis, 45% of which were non-Hispanic Black, 27% Hispanic, and 58% with a body mass index above 30 kg/m2. The 1-hour GCT was completed by 97% of participants, with 19% having a 1-hour GCT of 135 mg/dL or more.
The overall mean 24-hour glucose was 105.4 mg/dL, and the mean within-individual coefficient of variation was 17.1%. A median 94.5% of time was spent between 63 mg/dL and 140 mg/dL, compared to a median 4.3% of time spent above 140 mg/dL. The overall mean glucose levels during the daytime and nighttime were 103.2 mg/dL and 107.5 mg/dL respectively.
Composite neonatal outcomes were observed at a rate of 26%, the most common being required IV treatment for hypoglycemia with a rate of 14%. A TAR of 10% or more was observed in 18.5% of participants. These individuals had a 63% risk of composite adverse neonatal outcomes, compared to 19% in individuals with a TAR under 10%.
Adverse neonatal outcomes more likely in individuals with a TAR of 10% or more included LGA, required IV treatment for hypoglycemia, more hypoglycemia, and a longer length of stay.
These results indicated increased adverse neonatal outcomes from a CGM cutoff of 10% or more in individuals receiving screening for GDM. Investigators recommended interventional trials be conducted to determine if GDM can be diagnosed using CGM modalities and whether management based on TAR improves maternal and neonatal outcomes.
Reference
Fishel Bartal M, Ashby Cornthwaite J, Ghafir D. Continuous glucose monitoring in individuals undergoing gestational diabetes screening. American Journal of Obstetrics & Gynecology. 2023;229(4):441.E1-441.E14. doi:10.1016/j.ajog.2023.04.021
