During a Saturday, June 26, symposium at the Scientific Sessions, five experts addressed the utility of continuous glucose monitoring (CGM) during pregnancy.

Technology in Pregnancy—Continuous Glucose Monitoring (CGM) and Beyond can be viewed by registered meeting attendees at ADA2021.org through September 29, 2021. If you haven’t registered for the Virtual 81st Scientific Sessions, register today to access all of the valuable meeting content.

Kerstin Berntorp, MD, PhD, Professor and Senior Consultant, Department of Endocrinology, Skåne University Hospital, Lund University, Sweden, shared data from an observational cohort study of Swedish women with type 1 diabetes during pregnancy.

“Our data suggests for optimal neonatal outcomes, women and clinicians should aim for keeping blood glucose in the target range as early as possible during pregnancy,” said Dr. Berntorp, adding that the incidence of large for gestational age (LGA) birth weight increases when day-to-day control of blood glucose is not optimal.

In the study, LGA birth weight and neonatal composite outcomes were associated with high mean glucose levels and less time in range. The researchers found comparable outcomes in participants monitored by real-time CGM and intermittent CGM. Outcomes also appeared to be unaffected by the mode of insulin administration, Dr. Berntorp said.

Eleanor M. Scott, BM, BS, MD, FRCP, Professor of Diabetes and Maternal Health, University of Leeds, United Kingdom, described how glucose physiology changes over the course of pregnancy for women with type 1 diabetes and how these fluctuations relate to LGA.

The Continuous Glucose Monitoring in Women With Type 1 Diabetes in Pregnancy Trial (CONCEPTT), published in 2017, showed that real-time CGM in pregnancies complicated by type 1 diabetes improved maternal glucose control, reduced LGA from 69% to 53%, and improved neonatal health outcomes.

A functional data analysis of CONCEPTT and the Swedish observational study led by Dr. Berntorp identified temporal glucose variations that are not apparent from summary metrics, Dr. Scott noted. Using this analytic technique, researchers were able to view the 24-hour glucose profiles of the 380-plus participants of the two studies at a population level and determine the time periods when glucose is higher in women who have LGA—predominantly mealtimes—as well as the onset of high mean glucose levels associated with LGA.

“It highlights the crucial importance of achieving tight pregnancy glucose targets by 10 weeks gestation for normal fetal growth,” Dr. Scott said. “That’s far earlier than we’ve previously appreciated for reducing complications related to fetal hyperinsulinism.”

Claire L. Meek, MBChB, MRCP, FRCPath, PhD, Senior Clinical Research Fellow, Consultant, Diabetes in Pregnancy, and the Diabetes UK Harry Keen Intermediate Clinical Fellow, Institute of Metabolic Science, University of Cambridge, United Kingdom, compared CGM to the use of biomarkers to predict pregnancy outcomes.

Time in range, like A1C, has demonstrated good predictive ability for outcomes such as preterm birth, LGA, neonatal hypoglycemia, and neonatal intensive care unit admission, she said. When A1C cannot be measured, as has been the case for many patients during the COVID-19 pandemic, clinicians can rely on CGM data.

“The CGM metrics, particularly time in range and time above range, provide good prognostic information,” Dr. Meek said. “And actually, using both of these together gives good coverage in the first, second, and third trimesters.”

Time in range has been used to predict pregnancy outcomes earlier than other measurements—from 12 weeks gestation—while the predictive ability of A1C performs best in the later stages of pregnancy, she added. A novel biomarker, plasma glycated CD59 (gCD59), has been shown to provide strong neonatal outcome predictions at 24 weeks.

Dessi Zaharieva, PhD, Instructor, Stanford University, discussed the use of CGM in gestational diabetes (GDM), a condition that complicates 2% to 12% of pregnancies globally. She said CGM has the potential to help improve long-term outcomes for both the mother and fetus.

“CGM can provide a more comprehensive assessment of glycemia compared to self-monitoring of blood glucose (SMBG),” Dr. Zaharieva said. “In women with GDM, CGM can show greater hyperglycemia than SMBG, which can show more of a snapshot in time rather than a 24-hour overview of glycemic differences.”

CGM after diagnosis of GDM also has the potential to detect patients who would benefit from additional monitoring during pregnancy, as CGM can identify increased probability of the need for pharmacological treatment, she said.

Carol J. Levy, MD, CDCES, Associate Professor of Medicine and Obstetrics and Director, Mount Sinai Diabetes Center and Type 1 Diabetes Clinical Research, Icahn School of Medicine at Mount Sinai, discussed the reliability of CGM.

Outcomes data support the benefits of CGM during and outside of pregnancy, and endocrine organizations including the ADA support its use in pregnancies complicated by type 1 diabetes, she said. However, the U.S. Food and Drug Administration has not approved CGM in pregnancy. Canada has allowed CGM in pregnancy during the pandemic, while the United Kingdom covers CGM during pregnancy for women with type 1 diabetes.

Following encouraging results from accuracy studies, Dr. Levy said further research is needed to determine how to best utilize CGM to manage diabetes in pregnancy and to reduce the burden of self-care for this population.