Continuous glucose monitoring
Continuous glucose monitoring (CGM) enables determination of peak post-prandial glucose levels, mean glucose level, episodes of nocturnal hуреrglyϲaеmiа, and percent time in range (TIR) for a 24-hour period. It is widely recommended for pregnancies complicated by type 1 diabetes due to compelling data showing that even 4% to 7% improvements in TIR can result in an approximate 50% decrease in large for gestational age infants and neonatal intensive care unit (NICU) admissions.[3]American Diabetes Association. Standards of care in diabetes - 2025. Diabetes Care. 2025 Jan 1;48(Suppl 1):S344-52.
https://diabetesjournals.org/care/issue/48/Supplement_1
[108]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 Nov 25;390(10110):2347-59.
https://www.doi.org/10.1016/S0140-6736(17)32400-5
http://www.ncbi.nlm.nih.gov/pubmed/28923465?tool=bestpractice.com
CONCEPTT, a multicentre international randomised controlled trial, concluded that CGM should be offered to all pregnant women with type 1 diabetes using intensive insulin therapy.[108]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 Nov 25;390(10110):2347-59.
https://www.doi.org/10.1016/S0140-6736(17)32400-5
http://www.ncbi.nlm.nih.gov/pubmed/28923465?tool=bestpractice.com
Accordingly, the UK National Institute for Health and Care Excellence recommends offering CGM to all pregnant women with type 1 diabetes.[4]National Institute for Health and Care Excellence. Diabetes in pregnancy: management from preconception to the postnatal period. Dec 2020 [internet publication].
https://www.nice.org.uk/guidance/ng3
The data for type 2 diabetes and gestational diabetes mellitus (GDM) are more limited and conflicting and not sufficient to recommend TIR or mean glucose targets specific to these conditions.[109]American Diabetes Association. Standards of care in diabetes - 2024. Diabetes Care. 2024 Jan 1;47(Suppl 1):S314-21.
https://diabetesjournals.org/care/issue/47/Supplement_1
[110]Szmuilowicz ED, Barbour L, Brown FM, et al. Continuous glucose monitoring metrics for pregnancies complicated by diabetes: critical appraisal of current evidence. J Diabetes Sci Technol. 2024 Jul;18(4):819-34.
http://www.ncbi.nlm.nih.gov/pubmed/38606830?tool=bestpractice.com
[111]Battarbee AN, Durnwald C, Yee LM, et al. Continuous glucose monitoring for diabetes management during pregnancy: evidence, practical tips, and common pitfalls. Obstet Gynecol. 2024 Nov 1;144(5):649-59.
http://www.ncbi.nlm.nih.gov/pubmed/39016319?tool=bestpractice.com
The American Diabetes Association (ADA) notes that CGM can help to achieve haemoglobin A1c (HbA1c) targets in women with GDM when used in addition to pre- and post-prandial blood glucose monitoring. However, it concludes that data are insufficient to recommend CGM for all patients with GDM, and the decision to use CGM in these populations should be individualised.[3]American Diabetes Association. Standards of care in diabetes - 2025. Diabetes Care. 2025 Jan 1;48(Suppl 1):S344-52.
https://diabetesjournals.org/care/issue/48/Supplement_1
Research among women with GDM found that mothers who went on to deliver large-for-gestational-age (LGA) infants had higher overnight glucose levels during pregnancy compared with mothers without LGA infants, suggesting that detecting and addressing nocturnal glucose control may help to reduce rates of LGA infants in women with GDM. However, the study was unable to conclude whether CGM used throughout pregnancy reduces the risk of delivering a LGA infant.[112]Law GR, Alnaji A, Alrefaii L, et al. Suboptimal nocturnal glucose control is associated with large for gestational age in treated gestational diabetes mellitus. Diabetes Care. 2019 May;42(5):810-5.
https://www.doi.org/10.2337/dc18-2212
http://www.ncbi.nlm.nih.gov/pubmed/30765428?tool=bestpractice.com
One systematic review found evidence to suggest CGM is superior to self-monitoring of blood glucose among women with GDM in terms of detecting hypoglycaemic and hyperglycaemic episodes, which might result in an improvement of maternal and fetal outcomes.[113]Yu Q, Aris IM, Tan KH, et al. Application and utility of continuous glucose monitoring in pregnancy: a systematic review. Front Endocrinol (Lausanne). 2019;10:697.
https://www.doi.org/10.3389/fendo.2019.00697
http://www.ncbi.nlm.nih.gov/pubmed/31681170?tool=bestpractice.com
Larger sample sizes and complete pregnancy coverage is needed to determine the effectiveness of CGM in GDM.