Intelligent diabetes care designed for pregnancy

Use of continuous glucose monitoring (CGM) for gestational diabetes seems to be lagging behind the rest of the diabetes community. Pregnant patients are often the last to be included in research, and it can be difficult to shift practice protocols to accommodate new technology. Although CGM use has been proven to improve the quality of life in a person with diabetes (PWD), they are not regularly prescribed to patients with gestational diabetes.¹ 

It’s cumbersome for pregnant patients to keep a detailed blood sugar log. Nobody likes to do fingersticks. Readings get missed. Meals aren’t tracked. Paper logs get lost. And it’s a challenge for the obstetrics practice. It requires staff time to review the glucose logs and you are forced to make treatment decisions based on spotty data and rough meal estimates. 

CGMs could revolutionize gestational diabetes care. Between real-time feedback on treatment and meal impact and the ability to review overnight glucose levels—without sleep disruption, CGMs are a vital tool for managing diabetes. But can you use CGMs for gestational diabetes? Are they accurate? Keep reading to see how CGMs can be a valuable tool for women with gestational diabetes.

TL;DR: The latest CGMs from Dexcom and Abbott (Freestyle Libre) are proven accurate in pregnancy and a trusted method of monitoring glucose levels in gestational diabetes. Insurance coverage for CGM is also improving. However, CGMs require additional apps and tools to conform with ACOG guidelines.

CGM Use in Gestational Diabetes

CGMs capture real-time glucose data around the clock. This regular access to glucose trends allows for diet and insulin doses to be modified to reduce the incidence of both hyperglycemia and hypoglycemia. Not to mention that depending on the CGM system, there are fewer fingersticks, if any. But are CGMs accurate?

Are CGMs Accurate in Pregnancy?

Of course, accuracy of CGMs is a valid concern. Fortunately, recent clinical trials around CGM use in pregnancy have shown them to be accurate. But first, let’s address CGM’s accuracy overall. The mean absolute relative difference (MARD) is how the accuracy of CGM systems is measured. A lower number suggests greater accuracy, and a MARD <10% is considered acceptable.² 

Here are the MARD values for the most commonly used CGMs in gestational diabetes:

• Dexcom G7: 8.2%
• Freestyle Libre 2: 9.2%
• Freestyle Libre 3: 7.9%

When researchers compared real-time CGM (rtCGM) readings with samplings of venous blood at ~15 (+/- 5) minute intervals over a 6 hour period of time, over 83% of the CGM values were within 15% of the venous values.³

While their findings revealed the MARD was a bit higher on the first day of wear, the overall MARD was 9.5%—still within the acceptable range.

Intermittently scanned CGM (isCGM) is also accurate during pregnancy. Comparisons were made with pairs of fingerstick glucose levels and isCGM and were found to be clinically consistent.⁴ The difference between the two was about 16%, with the isCGM trending a bit lower in values. All are considered safe and accurate, which is why they have achieved approval.

Are CGMs Approved for Use in Gestational Diabetes?

Yes, CGMs are approved for use in GDM. CGM manufacturers must go through a systematic process to obtain Federal Drug Administration (FDA) approval for use in pregnancy.

First, preclinical studies are performed to evaluate the accuracy and safety of use. Additionally, clinical trials are conducted with pregnant women with gestational diabetes to assess performance and efficacy. Abbott and Dexcom have completed the process and received specific clearance for use in gestational diabetes. Currently approved CGMs include:

• Dexcom G7
• Freestyle Libre 2
• Freestyle Libre 3

While insurance coverage of CGMs for patients with GDM varies, many payors are starting to cover CGM. For example, California Medi-Cal now covers CGM for gestational diabetes and up to one year postpartum. Both FreeStyle and Dexcom have patient assistance programs to help lower costs in cases where insurance will not cover them.

So CGMs are approved and covered for GDM patients, but are the apps useful in pregnancy?

Do the CGM Apps Conform to ACOG Guidelines for Pregnancy?

Unfortunately, shortcomings in the design of CGM apps are an aspect of CGMs that limit their use in pregnancy.

One major difference between the data needs of diabetes in pregnancy and the non-pregnant population is the change in the target range. Most CGM apps and data outputs are reported according to the non-pregnant population (70-180 mg/dL as the target range). However, we know from the American College of Obstetrics and Gynecology (ACOG) that glucose targets are lower in pregnancy — 63-140 mg/dL. Settings are not easily adjusted to pregnancy-specific goals, and your patient’s CGM app may be showing them that they are in the “green”, when they are at a less desirable level for pregnancy.

Another key difference is that most OBGYNs and perinatologists prescribe therapy based on fasting and postprandial blood sugar values (with fasting target under 95 mg/dl and postprandial under 140 mg/dL for 1hr or 120 mg/dL for 2hr).  While CGM apps may let you note meal times, they do not automatically calculate fasting and postprandial values, or arrange them into daily logs that providers typically use.  

To make CGMs work well for gestational diabetes, pregnancy-specific digital health tools can help connect the dots.

LilyLink Provides Pregnancy-Specific Data

The founders of LilyLink saw how diabetes tech was not tailored for gestational diabetes care. In response, they designed the LilyLink platform under guidance from Maternal-Fetal Medicine (MFM) specialists to conform to diabetes management recommendations for pregnancy. 

The app is compatible with all pregnancy-approved CGMs, and users will see how their numbers stack up to the ACOG and American Diabetes Association (ADA) guidelines. Postprandial logging is automated and users can take pictures of their meals and enter exercise to play an active role in their GDM care. The provider then has direct access to CGM-generated digital logs and summary reports.

Example of a CGM-generated digital postprandial log

CGMs can be used for GDM and their use can better conform to ACOG guidelines with LilyLink’s end-to-end solution. The technology offers a promising tool for those managing GDM to improve maternal and fetal outcomes.

Easily Incorporate CGMS into Your Obstetrics Practice

CGM use in gestational diabetes has great potential to improve maternal and fetal outcomes, optimize glucose management, and enhance user acceptability in those with GDM. So far, what we know:

• CGMs are indeed accurate in pregnancy and can be a trusted method of monitoring glucose levels in gestational diabetes.
• Several CGMs have been indicated for use in GDM: Dexcom G7, FreeStyle Libre 2, and FreeStyle Libre 3.
• The CGM apps do not report data using the targets recommended by ACOG and ADA.
• The LilyLink app is designed for use in pregnancy and is optimized considering the data needs for this specific population.

Looking to incorporate CGMs into your OB practice? LilyLink can simplify the process with our end-end diabetes platform designed specifically for high-risk pregnancy care. Schedule a demo today.

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References

1. Johnston AR, Poll JB, Hays EM, Jones CW. Perceived impact of continuous glucose monitor use on quality of life and self-care for patients with type 2 diabetes. Diabetes Epidemiology and Management. 2022;6:100068. doi:10.1016/j.deman.2022.100068.
2. Heinemann L, Schoemaker M, Schmelzeisen-Redecker G, et al. Benefits and Limitations of MARD as a Performance Parameter for Continuous Glucose Monitoring in the Interstitial Space. J Diabetes Sci Technol. 2020;14(1):135-150. doi:10.1177/1932296819855670
3. Polsky S, Valent AM, Isganaitis E, et al. Performance of the Dexcom G7 Continuous Glucose Monitoring System in Pregnant Women with Diabetes. Diabetes Technol Ther. 2024;26(5):307-312. doi:10.1089/dia.2023.0516
4. Hussain FN, Raymond S, Feldman KM, et al. Comparison of an Intermittently Scanned (Flash) Continuous Glucose Monitoring System to Standard Self-Monitoring of Capillary Blood Glucose in Gestational Diabetes Mellitus. Am J Perinatol. 2023;40(11):1149-1157. doi:10.1055/a-2053-7650

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