Continuous glucose monitoring during pregnancy

A Review of Research Progress on Glycemic Variability and Gestational Diabetes

Gestational diabetes mellitus (GDM) is associated with many adverse obstetric outcomes and neonatal outcomes, including preeclampsia, Cesarean section, and macrosomia. Active screening and early diabetes control can reduce the occurrence of adverse outcomes. Glycosylated hemoglobin (HbA1c) only reflects average blood glucose levels, but not glycemic variability (GV). Studies have shown that GV can cause a series of adverse reactions, and good control of GV can reduce the incidence of adverse pregnancy outcomes in patients with GDM. In order to provide clinicians with a better basis for diagnosis and treatment, this study reviewed the measurement, evaluation, and control of GV, the importance of GV for patients with GDM, and correlations between GV and maternal and neonatal outcomes.

Application and Utility of Continuous Glucose Monitoring in Pregnancy: A Systematic Review

Background: In the past decade, continuous glucose monitoring (CGM) has been proven to have similar accuracy to self-monitoring of blood glucose (SMBG) and yet provides better therapy optimization and detects trends in glucose values due to higher frequency of testing. Even though the feasibility and utility of CGM has been proven successfully in Type 1 and 2 diabetes, there is a lack of knowledge of its application and effectiveness in pregnancy, especially in gestational diabetes mellitus (GDM). In this review, we aimed to summarize and evaluate the updated scientific evidence on the application of CGM in pregnancies complicated with GDM. Methods: A search using keywords related to CGM and GDM on PubMed was conducted and articles were filtered based on full text, year of publication (Jan 1998-Dec 2018), human subject studies, and written in English. Reviews and duplicate articles were removed. A final total of 29 articles were included in this review. Results: In terms of maternal and fetal outcomes, inconsistent evidence was reported. Among GDM patients using CGM and SMBG, two randomized controlled trials (RCTs) found no significant differences in macrosomia, birth weight (BW), and gestational age (GA) at delivery between these two groups, while one prospective cohort found a lower incidence of cesarean section and macrosomia in CGM use subjects. Furthermore, CGM use was consistently found to have increased detection in dysglycemia and glycemic variability compared to SMBG. In terms of clinical utility, CGM use led to more treatment adjustments and lower gestational weight gain (GWG). Lastly, CGM use showed higher postprandial glucose levels in GDM-complicated pregnancies than in normal pregnancies. Conclusion: Current updated evidence suggests that CGM is superior to SMBG among GDM pregnancies in terms of detecting hypoglycemic and hyperglycemic episodes, which might result in an improvement of maternal and fetal outcomes. In addition, CGM detects a wider glycemic variability in GDM mothers than non-GDM controls. Further research with larger sample sizes and complete pregnancy coverage is needed to explore the clinical utility such as screening and predictive values of CGM for GDM.

Utility of Continuous Glucose Monitoring in Type 1 and Type 2 Diabetes

A consensus conference of the American Association of Clinical Endocrinologists and American College of Endocrinology held in February 2016 advocated expanding the use of continuous glucose monitoring (CGM) in the management of diabetes. Based on the data described in this paper, CGM use is shown to improve glucose control and reduce hypoglycemic events, and therefore has the potential to reduce the risk of acute and chronic complications of diabetes. Likely, all of the above would not only improve the quality of life and life expectancy of people with diabetes, but would also have a positive impact on health-related cost.

A Study of the Carbohydrate-to-Insulin Ratio in Pregnant Women with Type 1 Diabetes on Pump Treatment

AIM

The aim of this study was to assess carbohydrate (CHO)-to-insulin ratio (CHO/IR) values in pregnant women with type 1 diabetes and to describe differences in CHO/IR across each week of pregnancy.

MATERIALS AND METHODS

This was a multicenter, retrospective, observational study (2006-2012) of 101 white pregnant women with a mean age of 32 (range, 18-43) years who had type 1 diabetes and were under continuous subcutaneous insulin infusion (CSII) therapy. These patients had the following characteristics: type 1 diabetes duration was 1 year (range, 1-31 years), the pregestational glycosylated hemoglobin level was 6.9% (range, 6.8-12.1%), the median weight gain during pregnancy was 14 kg (-3; 25 kg), with delivery at 37 weeks (range, 30-40 weeks), and the child had a birth weight of 3.530 kg (range, 1.480-5.250 kg). The CHO/IR was measured by dividing the CHO (in g) of each meal by insulin unit injected to acquire and maintain the following glycemic targets: fasting <90 mg/dL and 1-h postprandial <130 mg/dL. Simultaneously, CHO/IR indices were calculated through 500/total daily doses of insulin and 300/total daily doses of insulin. Education and management before and during pregnancy were in agreement with Italian Association of Dietitians, Association of Medical Diabetologists, and Italian Society of Diabetology recommendations. Data were analyzed using SPSS software (version 20.0; SPSS, Inc., Chicago, IL).

RESULTS

The CHO/IR decreased on average from 9.6 (5-18) to 5.4 (2.3-8) at breakfast, from 10 (3.5-16) to 8.4 (3.0-17.8) at lunch, and from 12.5 (8-20) to 6.1 (4.2-12) at dinner. The CHO/IR calculated using the "500 rule" decreased from 14.3 (10-20.3) to 8.6 (4.1-15.9). Using the "300 rule," the ratios decreased from 8.5 (6-12.1) to 5.2 (2.4-9.5). The bivariate correlation between the values calculated more appropriate values using the "300 rule" for breakfast and the "500 rule" for lunch and dinner across all weeks of pregnancy.

CONCLUSIONS

CHO/IR reduction in pregnancy is likely due to an increase in insulin resistance.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY 2016 OUTPATIENT GLUCOSE MONITORING CONSENSUS STATEMENT

This document represents the official position of the American Association of Clinical Endocrinologists and American College of Endocrinology. Where there were no randomized controlled trials or specific U.S. FDA labeling for issues in clinical practice, the participating clinical experts utilized their judgment and experience. Every effort was made to achieve consensus among the committee members. Position statements are meant to provide guidance, but they are not to be considered prescriptive for any individual patient and cannot replace the judgment of a clinician.

Continuous glucose monitoring effects on maternal glycemic control and pregnancy outcomes in patients with gestational diabetes mellitus: a prospective cohort study

CONTEXT

Clinical evidence on the consequential effects of continuous glucose monitoring (CGM) on pregnancy outcomes in women with gestational diabetes mellitus (GDM) is scarcely available.

OBJECTIVE

Our objective was to evaluate the effectiveness of CGM on maternal glycemic control and pregnancy outcomes in patients with GDM .

PATIENTS

In total, 340 Chinese pregnant women with GDM were allocated to either the routine care group (n = 190) or the CGM group (n =150).

DESIGN AND SETTING

This was a prospective cohort study in the Department of Obstetrics of GuangDong Women and Children Hospital in China. Recruitment started in April 2011 and stopped in August 2012.

INTERVENTIONS

A 72-hour CGM system was used as a supplementary tool for glucose monitoring in the CGM group. PRIMARY OUTCOME MEASUREMENTS: The parameters of glycemic variability included mean blood glucose, the SD of blood glucose, mean amplitude of glycemic excursions (MAGEs), and the mean of daily differences. The maternal outcomes (preeclampsia and cesarean delivery) and composite neonatal outcomes were analyzed.

RESULTS

The SD of blood glucose, MAGEs, and mean of daily differences values were significantly lower in the CGM group compared with those of the routine care group (P < .001). Subjects in the CGM group were at lower risk of preeclampsia and primary cesarean delivery compared with the routine care group (P < .05). The mean infant birth weight of women in the CGM group was lower than infants of women in the routine care group (P < .001). The MAGE was associated with birth weight (β = 0.196, P < .001), and it was an independent factor for preeclampsia (odds ratio, 3.66; 95% confidence interval 2.16-6.20) and composite neonatal outcome (odds ratio, 1.34; 95% confidence interval 1.01-1.77).

CONCLUSIONS

The use of supplementary CGM combined with routine antenatal care can improve the glycemic control and pregnancy outcomes of patients with GDM.

Shape information in repeated glucose curves during pregnancy provided significant physiological information for neonatal outcomes

Objective

To use multilevel functional principal component analysis to exploit the information inherent in the shape of longitudinally sampled glucose curves during pregnancy, and to analyse the impact of glucose curve characteristics on neonatal birth weight, percentage fat and cord blood C-peptide.

Study Design and Setting

A cohort study of healthy, pregnant women (n = 884). They underwent two oral glucose tolerance tests (gestational weeks 14–16 and 30–32), which gave two glucose curves per woman.

Results

Glucose values were higher, and peaked later in third trimester than in early pregnancy. The curve characteristic “general glucose level” accounted for 91% of the variation across visits, and 72% within visits. The curve characteristics “timing of postprandial peak”, and “oscillating glucose levels” accounted for a larger part of the variation within visits (15% and 8%), than across visits (7% and <2%). A late postprandial peak during pregnancy, and high general glucose levels in third trimester had significant, positive effects on birth weight (p<0.05). Generally high glucose levels during pregnancy had a significant, positive impact on neonatal percentage fat (p = 0.04). High general glucose level in third trimester had a significant, positive impact on cord blood C-peptide (p = 0.004).

Conclusion

Shape information in entire OGTT curves provides significant physiological information of importance for several outcomes, and may contribute to the understanding of the metabolic changes during pregnancy.

Experiences of continuous subcutaneous insulin infusion in pregnant women with type 1 diabetes during delivery from four Italian centers: a retrospective observational study

OBJECTIVES

An optimized metabolic control during delivery is mandatory to prevent maternal-neonatal complications. The primary aim of this study was to evaluate the efficacy and safety of continuous subcutaneous insulin infusion (CSII) during delivery in pregnant women with type 1 diabetes. The secondary aim was to assess the impact of real-time continuous glucose monitoring (RT-CGM) added to CSII versus CSII alone.

RESEARCH DESIGN AND METHODS

This was a multicenter observational retrospective study. A standardized protocol, to use CSII throughout pregnancy and delivery, foresaw three different insulin basal rates according to blood glucose level: profile A, the last basal rate in use; profile B, preventive 50% reduction of the last basal rate in use; and profile C, 0.1-0.2 U/h for blood glucose level <70 mg/dL, activated just before anesthesia or at the beginning of active labor. An alternative intravenous protocol (IVP) was given in case of complications and relevant metabolic deterioration. Blood glucose in the target range (70-140 mg/dL) throughout delivery and percentage of activation of the IVP were primary outcomes.

RESULTS

Sixty-five pregnant women with diabetes included in the study (56-86% cesarean section; 9-14% spontaneous/stimulated vaginal delivery). Mean blood glucose level was 102 ± 31 mg/dL at 0 min, 109 ± 42 mg/dL at 30 min, 120 ± 48 mg/dL at 60 min, and 99 ± 34 mg/dL at 24 h. Mean basal rate during delivery was 0.6 ± 0.4 U/h (profile B). Mean capillary blood glucose (CBG) level was lower in the RT-CGM group relative to the CSII-alone group: 80 ± 14 mg/dL versus 111 ± 32 mg/dL at 0 min (P<0.01), 79 ± 11 mg/dL versus 109 ± 42 mg/dL at 30 min (P<0.02), and 98 ± 20 mg/dL versus 125 ± 51 mg/dL at 60 min (difference not significant). Eleven newborns experienced transient neonatal hypoglycemia. None of the women switched to IVP. No major differences were observed according to delivery procedure.

CONCLUSIONS

CSII is possible and safe in different types of delivery in selected and educated women. RT-CGM helps to obtain better outcomes in terms of maternal peripartum CBG level.

Accuracy of continuous glucose monitoring during exercise in type 1 diabetes pregnancy

BACKGROUND

Performance of continuous glucose monitors (CGMs) may be lower when glucose levels are changing rapidly, such as occurs during physical activity. Our aim was to evaluate accuracy of a current-generation CGM during moderate-intensity exercise in type 1 diabetes (T1D) pregnancy.

SUBJECTS AND METHODS

As part of a study of 24-h closed-loop insulin delivery in 12 women with T1D (disease duration, 17.6 years; glycosylated hemoglobin, 6.4%) during pregnancy (gestation, 21 weeks), we evaluated the Freestyle Navigator(®) sensor (Abbott Diabetes Care, Alameda, CA) during afternoon (15:00-18:00 h) and morning (09:30-12:30 h) exercise (55 min of brisk walking on a treadmill followed by a 2-h recovery), compared with sedentary conditions (18:00-09:00 h). Plasma (reference) glucose, measured at regular 15-30-min intervals with the YSI Ltd. (Fleet, United Kingdom) model YSI 2300 analyzer, was used to assess CGM performance.

RESULTS

Sensor accuracy, as indicated by the larger relative absolute difference (RAD) between paired sensor and reference glucose values, was lower during exercise compared with rest (median RAD, 11.8% vs. 18.4%; P<0.001). These differences remained significant when correcting for plasma glucose relative rate of change (P<0.001). Analysis by glucose range showed lower accuracy during hypoglycemia for both sedentary (median RAD, 24.4%) and exercise (median RAD, 32.1%) conditions. Using Clarke error grid analysis, 96% of CGM values were clinically safe under resting conditions compared with only 87% during exercise.

CONCLUSIONS

Compared with sedentary conditions, accuracy of the Freestyle Navigator CGM was lower during moderate-intensity exercise in pregnant women with T1D. This difference was particularly marked in hypoglycemia and could not be solely explained by the glucose rate of change associated with physical activity.

Continuous glucose monitoring: current clinical use

Four kinds of subcutaneous continuous glucose monitoring (CGM) machines have been currently introduced in clinical practice. These machines exhibit real-time glucose on the monitor every 5 minutes and have alarms to indicate hypoglycaemia and hyperglycaemia. However, thus far, there is no clear consensus about the clinical indications for CGM in actual clinical practice. CGM should be an ideal and powerful tool for monitoring glucose variability. Glycaemic variability has become a major concern over the years with growing evidence on its detrimental impact with respect to the risk of diabetic complications. Although the HbA1c level is ubiquitously measures in clinical practice, this level does not adequately represent glycaemic variability. Currently available evidence indicates that CGM aids in lowering the HbA1c level without increasing the incidence of severe hypoglycaemic episodes in patients with type 1 diabetes. Thus far, CGM has not been indicated for preventing severe hypoglycaemia or for treating type 2 diabetes because sufficient supporting evidence has not been obtained. Promising results have been obtained for the use of CGM for pregnant women with diabetes and for patients with hospital hyperglycaemia. Predictions regarding the feasibility of the closed-loop system have proven to be optimistic. CGM-integrated communication systems using information technology such as smart phone help controlling blood glucose more easily and effectively.

Closed-loop insulin delivery during pregnancy complicated by type 1 diabetes

OBJECTIVE

This study evaluated closed-loop insulin delivery with a model predictive control (MPC) algorithm during early (12-16 weeks) and late gestation (28-32 weeks) in pregnant women with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Ten women with type 1 diabetes (age 31 years, diabetes duration 19 years, BMI 24.1 kg/m(2), booking A1C 6.9%) were studied over 24 h during early (14.8 weeks) and late pregnancy (28.0 weeks). A nurse adjusted the basal insulin infusion rate from continuous glucose measurements (CGM), fed into the MPC algorithm every 15 min. Mean glucose and time spent in target (63-140 mg/dL), hyperglycemic (>140 to ≥ 180 mg/dL), and hypoglycemic (<63 to ≤ 50 mg/dL) were calculated using plasma and sensor glucose measurements. Linear mixed-effects models were used to compare glucose control during early and late gestation.

RESULTS

During closed-loop insulin delivery, median (interquartile range) plasma glucose levels were 117 (100.8-154.8) mg/dL in early and 126 (109.8-140.4) mg/dL in late gestation (P = 0.72). The overnight mean (interquartile range) plasma glucose time in target was 84% (50-100%) in early and 100% (94-100%) in late pregnancy (P = 0.09). Overnight mean (interquartile range) time spent hyperglycemic (>140 mg/dL) was 7% (0-40%) in early and 0% (0-6%) in late pregnancy (P = 0.25) and hypoglycemic (<63 mg/dL) was 0% (0-3%) and 0% (0-0%), respectively (P = 0.18). Postprandial glucose control, glucose variability, insulin infusion rates, and CGM sensor accuracy were no different in early or late pregnancy.

CONCLUSIONS

MPC algorithm performance was maintained throughout pregnancy, suggesting that overnight closed-loop insulin delivery could be used safely during pregnancy. More work is needed to achieve optimal postprandial glucose control.

Technology and pregnancy

In the USA, depending upon the diagnosis criteria used, 135,000-200,000 women annually develop gestational diabetes mellitus, adding to the number of pregnant women already suffering from either type 1 or type 2 diabetes. Maternal hyperglycaemia and the resultant fetal hyperinsulinaemia are central to the pathophysiology of diabetic complications of pregnancy. These complications include congenital malformations and an increase in neonatal intensive care unit admission and birth trauma. In addition, there is an increased rate of accelerated fetal growth, neonatal metabolic complications and risk for stillbirth. Importantly, during the last century there were two breakthroughs in diabetes management and monitoring that changed the course of treatment: the discovery of insulin and the progress in the understanding of glucose monitoring. As technology has evolved, both glucose monitoring and insulin administration can now be achieved in a continuous fashion. In this review of the literature we focus on the utility of new technologies in the management and monitoring of diabetes in pregnancy.

Approach to the patient with diabetes during pregnancy

The epidemics of obesity and type 2 diabetes mellitus (T2DM) globally are paralleling an increase in the number of women with T2DM becoming pregnant. Because T2DM is frequently undiagnosed before pregnancy, the risk of major malformations in the developing fetus is increased due to uncontrolled hyperglycemia. The lack of preconception care and the increase in complications of pregnancy due to the coexistence of obesity and T2DM are of concern from both an individual and a public health standpoint. Rapid achievement of normoglycemia with limited weight gain is critical to optimize maternal and fetal outcomes in all women with diabetes during pregnancy, regardless of the type of diabetes. This article will focus on T2DM preceding pregnancy due to its increasing prevalence and potentially dire fetal and maternal consequences. Euglycemia before, during, and after all pregnancies complicated by diabetes results in the best opportunity for optimal outcomes for mother and infant.

Glucose monitoring during pregnancy

Self-monitoring of blood glucose in women with mild gestational diabetes has recently been proven to be useful in reducing the rates of fetal overgrowth and gestational weight gain. However, uncertainty remains with respect to the optimal frequency and timing of self-monitoring. A continuous glucose monitoring system may have utility in pregnant women with insulin-treated diabetes, especially for those women with blood sugars that are difficult to control or who experience nocturnal hypoglycemia; however, continuous glucose monitoring systems need additional study as part of larger, randomized trials.

Biochemical changes in urine and plasma of rats in food chain-mediated cadmium toxicity

The present study sets out to assess the toxicity of cadmium (Cd) administered via the food chain. The food chain was mimicked by exposing rats to diet containing milled Cd-exposed catfish as the source of protein. The toxicity of Cd was monitored by the determination of indices of oxidative stress and kidney dysfunction in plasma and urine of the rats after 1- and 3-month exposure periods. The results obtained indicate that Cd exposure in the rats was followed by marked accumulation of the metal in the liver and kidney with time. However, the kidney accumulated more Cd relative to the liver after both exposure periods. The levels of glucose, creatinine and lipid peroxidation were significantly (p < 0.05) increased in both plasma and urine of the rats after 1 month of exposure. Conversely, rats fed the test diet for 3 months had significantly (p < 0.05) decreased level of lipid peroxidation in the plasma and urine. However, the plasma and urine glucose concentrations were restored to levels not significantly (p > 0.05) different from control in rats fed the test diet for 3 months. Similarly, after 3 months, the creatinine level in the plasma was also restored to a level not significantly (p > 0.05) different from that of the control but was significantly (p < 0.05) elevated in the urine. A significant increase in urine protein concentration was demonstrated after 1-month exposure to Cd, but no significant change occurred in the plasma. Rats fed diet containing the Cd-incorporated fish for 3 months also had no significant (p > 0.05) change in plasma and urine protein concentrations. These results suggest that this route of exposure caused kidney impairment, oxidative stress as well as alteration in glucose metabolism after 1 month but not after 3 months, possibly due to adaptation occasioned by the antioxidative defense armory of the rats.

Continuous glucose monitoring health outcomes

Continuous glucose monitoring (CGM) is a new tool that has recently become available to people with diabetes. Properly designing and conducting trials in order to answer important questions regarding the clinical usefulness of CGM is very difficult and fraught with many confounding variables and unique challenges. Initial clinical trials using older technology using retrospective data analysis have not shown unequivocal benefit; however, more recent data using real-time CGM suggest significant improvements in important clinical outcomes such as hemoglobin A1c, time spent in the hypo- and hyperglycemic range, glucose variability, quality of life, and perceived value to physicians and patients. Additional variables such as age of the subject and duration of sensor use have important implications in defining the benefits of CGM in a heterogeneous population with diabetes. This review will present the most relevant recent literature and comment on the methodological difficulties that have made this field challenging.

Clinical experience with continuous glucose monitoring in adults

Despite recent advances in therapy, achieving adequate glycemic control may be difficult for a large number of patients with diabetes. Real-time (RT)-continuous glucose monitoring (CGM) has the potential to improve glycemic control through immediate feedback to the properly trained patient. However, limitations exist both in interpreting the results of published randomized clinical trials on CGM use and in extrapolating the results to the diabetes population at large. This review summarizes the evidence for use, identifies suitable candidates, describes optimal implementation, and employs case scenarios in order to emphasize practical aspects of RT-CGM use in adults. Establishment of expectations and comprehensive education in intensive insulin therapy and RT-CGM use are necessary for successful implementation. Because the technology has been shown to be most useful in patients who are actively viewing and responding to RT data, patients should receive explicit instructions for active self-adjustment of insulin and lifestyle elements. While the technology is improving, false alarms remain a significant barrier to optimal use. The utility of RT-CGM for patients with severe hypoglycemia or hypoglycemia unawareness has not been established. Finally, studies are needed to determine the sustainability of improvements in glycemic control, as well as cost-effectiveness and practicality of implementation into busy real-world practice.