Time in Range and Pregnancy Outcomes in People with Diabetes Using Continuous Glucose Monitoring

Continuous Glucose Monitoring Metrics for Pregnancies Complicated by Diabetes: Critical Appraisal of Current Evidence

Ascertaining the utility of continuous glucose monitoring (CGM) in pregnancy complicated by diabetes is a rapidly evolving area, as the prevalence of type 1 diabetes (T1D), type 2 diabetes (T2D), and gestational diabetes mellitus (GDM) escalates. The seminal randomized controlled trial (RCT) evaluating CGM use added to standard care in pregnancy in T1D demonstrated significant improvements in maternal glycemia and neonatal health outcomes. Current clinical guidance recommends targets for percentage time in range (TIR), time above range (TAR), and time below range (TBR) during pregnancy complicated by T1D that are widely used in clinical practice. However, the superiority of CGM over blood glucose monitoring (BGM) is still questioned in both T2D and GDM, and whether glucose targets should be different than in T1D is unknown. Questions requiring additional research include which CGM metrics are superior in predicting clinical outcomes, how should pregnancy-specific CGM targets be defined, whether CGM targets should differ according to gestational age, and if CGM metrics during pregnancy should be similar across all types of diabetes. Limiting the potential for CGM to improve pregnancy outcomes may be our inability to maintain TIR > 70% throughout gestation, a goal achieved in the minority of patients studied. Adverse pregnancy outcomes remain high in women with T1D and T2D in pregnancy despite CGM technology, and this review explores the potential reasons and questions yet to be investigated.

Continuous glucose monitoring in pregnancies with type 1 diabetes: small increases in time-in-range improve maternal and perinatal outcomes

BACKGROUND

Continuous glucose monitors provide detailed information regarding glycemic control in pregnant patients with type 1 diabetes. Little data have been published examining the association between continuous glucose monitor parameters and perinatal outcomes among gravidas with type 1 diabetes using continuous glucose monitors.

OBJECTIVE

This study aimed to examine the association between perinatal outcomes and time-in-range as assessed by continuous glucose monitors used in pregnant individuals with type 1 diabetes. We hypothesized that higher time-in-range would be associated with lower risk of adverse perinatal outcomes.

STUDY DESIGN

This multicenter retrospective cohort study included all gravidas with type 1 diabetes using continuous glucose monitors who delivered from 2020 to 2022 at 5 University of California sites. Only those with continuous glucose monitor target range set to 70 to 140 mg/dL (±10 mg/dL) were included. Time-in-range (%) was recorded at 12, 16, 20, 24, 28, and 32 weeks. The primary maternal and neonatal outcomes were preeclampsia and large for gestational age, defined as birthweight ≥95th percentile. Kruskal-Wallis tests were used to compare median time-in-range between those with and without the primary outcomes. Log-binomial regression was used to obtain risk ratios, with adjustment for microvascular disease and years with type 1 diabetes.

RESULTS

A total of 91 patients were included. Most used an insulin pump (81%) and did not have diabetic microvascular disease (72%). Median time since diagnosis of type 1 diabetes was 16 years, and median periconception hemoglobin A1c was 6.7%. Compared with those with preeclampsia, normotensive gravidas had significantly higher time-in-range at nearly every time point. A similar pattern was observed for those with normal-birthweight infants compared with large-for-gestational-age infants. On adjusted analyses, every 5-unit increase in time-in-range at 12 weeks was associated with 45% and 46% reductions in the risks of preeclampsia and large for gestational age, respectively (preeclampsia: adjusted risk ratio, 0.55; 95% confidence interval, 0.30-0.99; large for gestational age: adjusted risk ratio, 0.54; 95% confidence interval, 0.29-0.99).

CONCLUSION

Higher time-in-range is associated with lower risk of preeclampsia and large for gestational age. This association is observed early in gestation, when each 5-unit increase in time-in-range is associated with ∼50% reduction in the risk of these complications. These findings can be used to counsel patients regarding the risk of pregnancy complications at specific time-in-range values, and to encourage patients that even small improvements in time-in-range can have significant impact on pregnancy outcomes. Larger studies are needed to further explore these findings and to identify optimal time-in-range to reduce perinatal complication rates.

Advances in diabetes management: have pregnancy outcomes in women with type 1 diabetes changed in the last decades?

AIMS

Over the recent years multiple therapeutic and management opportunities have been made available to treat pregnant women with Type 1 diabetes (T1DM). However, analyses assessing whether these different approaches may have any specific advantage/disadvantage in metabolic control and neonatal outcomes is still limited. The aim of this study was to compare metabolic control and neonatal outcomes in pregnant women with T1DM among different basal insulins (NPH vs. analogue), insulin administration ways [Multiple Daily Injections (MDI) vs. Continuous Subcutaneous Insulin Infusion (CSII)] and glucose monitoring systems [Self-Monitoring of Blood Glucose (SMBG) vs. real-time/intermittently scanned Continuous Glucose Monitoring (rtCGM/isCGM)].

METHODS

A retrospective analysis on metabolic data and neonatal outcomes of 136 T1DM pregnant women (76% on MDI, based on NPH (51%) or analogue (49%); 24% on CSII; 24% using rtCGM/isCGM), managed between 2008 and 2020, was performed, comparing different therapeutic approaches.

RESULTS

Metabolic data and neonatal outcomes were comparable among women treated with different basal insulins. Women on CSII planned their pregnancy more frequently (82 vs. 60%; p = 0.043) and had better pregestational HbA1c (52 ± 5 vs. 60 ± 13 mmol/mol; p = 0.044) and first trimester HbA1c (48 ± 4 vs. 51 ± 8 mmol/mol; p = 0.047). Pregestational and first trimester HbA1c were also lower in women using rtCGM/isCGM (53 ± 8 vs. 58 ± 13 mmol/mol; p = 0.027 and 46 ± 5 vs. 51 ± 7 mmol/mol; p = 0.034, respectively). In the whole cohort, LGA risk was directly correlated to HbA1c at third trimester (correlation coefficient: 0.335, p = 0.001) and inversely correlated to the achievement of HbA1c target (≤6% [<42 mmol/mol]) at third trimester (correlation coefficient: - 0.367, p < 0.001).

CONCLUSION

Treatment with insulin analogs didn't significantly change metabolic control and neonatal outcomes in T1DM women, while CSII and rtCGM/isCGM can optimize preconception and first trimester pregnancy glycemic control. Irrespective of the therapeutic management, third trimester HbA1c remains the strongest risk factor for LGA.

Continuous glucose monitor use in type 2 diabetes mellitus in pregnancy and perinatal outcomes: a systematic review and meta-analysis

OBJECTIVE

This study aimed to assess whether continuous glucose monitor use in type 2 diabetes mellitus in pregnancy is associated with improved perinatal outcomes.

DATA SOURCES

We searched Ovid MEDLINE, Scopus, ClinicalTrials.gov, and Cochrane library from inception through May 9, 2022.

STUDY ELIGIBILITY CRITERIA

We included all studies that compared continuous glucose monitor use with fingerstick glucose monitoring in women with type 2 diabetes mellitus.

METHODS

The initial search yielded 2463 unique citations that were screened in Covidence by 2 independent reviewers. Study types included randomized controlled trials, cohort studies, and cross-sectional studies. Our outcomes of interest were macrosomia or large-for-gestational-age infants, hemoglobin A1c, cesarean delivery, hypertensive disorders of pregnancy including preeclampsia, gestational age at delivery, and neonatal hypoglycemia.

RESULTS

Three randomized controlled trials met the inclusion criteria. We performed random-effects meta-analyses of estimates from 2 studies without risk of significant bias and reported summary adjusted odds ratios and 95% confidence intervals. Meta-analysis of 56 women with continuous glucose monitor use and 53 control women without continuous glucose monitor use showed that there was no difference in the incidence of large-for-gestational-age infants between continuous glucose monitor users and standard-of-care controls (odds ratio, 0.78; 95% confidence interval, 0.34-1.78) with an I2 of 0%. In addition, there was no difference in the development of preeclampsia between continuous glucose monitor users and standard-of-care controls (odds ratio, 1.63; 95% confidence interval, 0.34-7.22) with an I2 of 0%.

CONCLUSION

Continuous glucose monitor use was not associated with improved perinatal outcomes as assessed by large-for-gestational-age infants and preeclampsia. This review is limited by the small amount of data available for this population, and further research is needed.

Expanding the Role of Continuous Glucose Monitoring in Modern Diabetes Care Beyond Type 1 Disease

Application of continuous glucose monitoring (CGM) has moved diabetes care from a reactive to a proactive process, in which a person with diabetes can prevent episodes of hypoglycemia or hyperglycemia, rather than taking action only once low and high glucose are detected. Consequently, CGM devices are now seen as the standard of care for people with type 1 diabetes mellitus (T1DM). Evidence now supports the use of CGM in people with type 2 diabetes mellitus (T2DM) on any treatment regimen, not just for those on insulin therapy. Expanding the application of CGM to include all people with T1DM or T2DM can support effective intensification of therapies to reduce glucose exposure and lower the risk of complications and hospital admissions, which are associated with high healthcare costs. All of this can be achieved while minimizing the risk of hypoglycemia and improving quality of life for people with diabetes. Wider application of CGM can also bring considerable benefits for women with diabetes during pregnancy and their children, as well as providing support for acute care of hospital inpatients who experience the adverse effects of hyperglycemia following admission and surgical procedures, as a consequence of treatment-related insulin resistance or reduced insulin secretion. By tailoring the application of CGM for daily or intermittent use, depending on the patient profile and their needs, one can ensure the cost-effectiveness of CGM in each setting. In this article we discuss the evidence-based benefits of expanding the use of CGM technology to include all people with diabetes, along with a diverse population of people with non-diabetic glycemic dysregulation.