Continuous glucose monitoring lowers HbA1c and LGA risk in pregnancy

Continuous glucose monitoring lowers HbA1c and LGA risk in pregnancy | Image Credit: © Andrey Popov - © Andrey Popov - stock.adobe.com.

Hemoglobin A_1c levels are reduced by continuous glucose monitoring (CGM) vs self-monitoring of blood glucose, alongside a potential reduction in large for gestational age (LGA) risk, according to a recent study published in the American Journal of Obstetrics & Gynecology.¹

Over 17% of live births annually are impacted by diabetes in pregnancy (DIP), with increased risks of stillbirth, congenital malformations, LGA, and other complications. Glucose management is often accomplished through self-monitoring of blood glucose (SMBG), but data has indicated improved outcomes when adding CGM.²

“Despite increasing interest in the use of CGM in [type 2 diabetes (T2D)] and [gestational diabetes mellitus (GDM)], it is uncertain whether similar benefits in pregnancy outcomes are seen,” wrote investigators.¹

CGM vs SMBG assessment

The systematic review and meta-analysis were conducted to compare outcomes of CGM vs SMBG for managing DIP. Articles published from January 2003 to August 2024 were obtained through systematic searches of the Embase, Medline, CINAHL, CENTRAL, and Scopus databases.

Studies with participants using CGM for type 1 diabetes (T1D), T2D, or GDM with an SMBG comparator group were included in the analysis. Reporting maternal glycemia or perinatal outcomes was also required for inclusion. Exclusion criteria included non-pregnant patients, the absence of a comparator SMBG group, and the study being conducted in an inpatient setting.

Two independent study authors extracted study and participant characteristics, consulting a third author to resolve discrepancies. Cohort characteristics, participant characteristics, CGM data, and outcomes were extracted for assessment, along with links between CGM metrics and perinatal outcomes.

HbA_1c reduction across diabetes types

There were 18 studies included in the final analysis, 14 of which were randomized controlled trials (RCTs) and 4 were quasi-experimental. Three CGM methods were reported across these studies, including real-time CGM in 6, intermittently scanned CGM in 5, and retrospective CGM in 6. A mix of real-time CGM and intermittently scanned CGM was used by 1 study.

Reduced third-trimester HbA_1c was reported for DIP following CGM vs SMBG in a meta-analysis of 7 RCTs, with a mean difference (MD) of -0.22%. An improvement from CGM was also reported in quasi-experimental data, but the evidence had low certainty.

Another RCT highlighted reduced third-trimester HbA_1c from CGM vs SMBG in patients with T1D, with an MD of -0.18% Quasi-experimental data indicated an MD of -0.30%, supporting this association. However, no differences between CGM and SMBG were reported across 2 studies assessing third-trimester HbA_1c in T2D patients.

For mixed DIP, the MD in third-trimester HbA_1c for CGM vs SMBG across 4 RCTs was -0.60%, highlighting a reduction. A decline in third-trimester HbA_1c was also reported for GDM across 7 RCTs, with an MD of -0.18%.

Perinatal outcomes and LGA risk

Associations were reported for CGM glucose metrics and LGA. Specifically, reduced LGA was reported in patients with first-trimester CGM use and lower mean sensor glucose (SG), with an odds ratio (OR) of 1.04. A single trial showed benefits toward LGA when using CGM for pregnancy duration, reporting an OR of 0.54.

A decline in neonatal hypoglycemia based on an OR of 0.56 was also reported for CGM vs SMBG across 2 RCTs. Small for gestational age odds were not influenced by the method of glucose monitoring used. Overall, the results highlighted reduced third-trimester HbA_1c and mean SG from CGM use in T1D and GDM, leading to a decrease in LGA.

“Ongoing studies including RCTs of CGM use in T2D and GDM… as well as observational studies… alongside health economic analyses, will provide important insights into the role of CGM use in the management of both T2D and GDM, and in the prediction of GDM and perinatal complications more broadly,” wrote investigators.

References

1. Burk J, Ross GP, Hernandez TL, Colagiuri S, Sweeting A. Evidence for improved glucose metrics and perinatal outcomes with continuous glucose monitoring compared to self-monitoring in diabetes during pregnancy. American Journal of Obstetrics & Gynecology. 2025;233(3):162-175). doi:10.1016/j.ajog.2025.04.010
2. Feig DS, Donovan LE, Corcoy R, et al. Continuous glucose monitoring in pregnant women with type 1 diabetes (CONCEPTT): a multicentre international randomised controlled trial. Lancet. 2017;390(10110):2347-2359. doi:10.1016/S0140-6736(17)32400-5