Editor's Pick
Journal: Lancet (London, England) 2018;390(10110):2347-2359
PMID: 28923465
Pregnant women with type 1 diabetes face a higher risk of complications because their blood sugar levels can change quickly during pregnancy. Poor blood sugar control during pregnancy can affect both the mother and the baby, increasing the risk of complications such as large birth weight, premature birth, or low blood sugar in newborns. Continuous glucose monitoring (CGM) devices measure blood sugar levels throughout the day and night and may help people with diabetes manage their blood sugar more effectively. The aim of this randomised control trial was to determine whether using a continuous glucose monitor (CGM) in addition to standard blood sugar monitoring could improve blood sugar control in mothers and lead to better health outcomes for their babies.
The results showed that women who used CGM spent more time within their target blood sugar range during pregnancy compared with those using standard monitoring alone. Importantly, babies born to mothers using CGM had better health outcomes, including a lower risk of being born very large for their gestational age, fewer admissions to neonatal intensive care units, and reduced rates of newborn hypoglycaemia.
In conclusion, using CGM during pregnancy can improve blood sugar management and reduce certain risks for newborns in women with type 1 diabetes. Healthcare professionals can use these findings to support the use of CGM as part of diabetes management during pregnancy to improve both maternal and neonatal health outcomes.
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• In this study, pregnant women with type 1 diabetes reported improved glucose control, more time spent within the target glucose range, and had less glycaemic variability by 34 weeks.
• CGM was linked to fewer infants being large for gestational age, less neonatal hypoglycaemia, fewer NICU admissions, and a shorter hospital stay.
Introduction:
A randomised controlled trial was conducted in women aged 18–40 years with type 1 diabetes receiving intensive insulin therapy, to evaluate the effectiveness of continuous glucose monitoring (CGM) on maternal glucose control, as well as obstetric and neonatal health outcomes.
Methods:
325 women (215 pregnant and 110 planning pregnancy) were randomly assigned to either: CGM plus standard finger-prick capillary glucose testing group or a capillary glucose testing only group. Participants in both groups were advised to test their glucose levels at least seven times a day (before meals, 1–2 hours after meals, and before bed) and were given written instructions on how to use measurements to adjust insulin doses, customised according to their method of insulin delivery.
The primary outcomes were changes in HbA1c from randomisation to 34 weeks’ gestation in pregnant women, and to 24 weeks or conception in women planning pregnancy. Secondary outcomes included time spent within target glucose range, hypoglycaemia, maternal complications, and neonatal outcomes such as large-for-gestational-age birth, neonatal hypoglycaemia, neonatal ICU admission, and length of hospital stay.
Results
• A difference in HbA1c was reported in pregnant women using CGM compared with those using standard monitoring (mean difference −0·19%; 95% CI −0·34 to −0·03; p=0·02).
• Pregnant women using CGM spent more time within the target glucose range (68% vs 61%, p=0.003) and less time in hyperglycaemia (27% vs 32%, p=0.028) than the control group .
• Pregnant CGM users had fewer episodes of severe hypoglycaemia than the control group (18 v 21) but this was not significant.
Infants of CGM mothers.
• Lower rates of large-for-gestational-age births were reported (odds ratio 0·51, 95% CI 0·28–0·90; p=0.021).
• There were fewer neonatal intensive care admissions lasting more than 24 hours (odds ratio 0·48, 95% CI 0·26–0·86; p=0.016).
• There were fewer cases of neonatal hypoglycaemia requiring treatment with intravenous dextrose (0·45, 0·22–0·89; p=0.025).
• Hospital stays were shorter (p=0.009)
Conclusion:
CGM use during pregnancy in women with type 1 diabetes receiving intensive insulin therapy leads to better glucose control and improved neonatal outcomes.
• Although the change in HbA1c in this study was small, clinicians should consider that CGM users spent more time within the target glucose range and less time in hyperglycaemia.
• Better neonatal outcomes in mothers with type 1 diabetes using intensive insulin therapy and CGM need to be considered; offering CGM to women with type 1 diabetes in early pregnancy may be worthwhile.
• CGM is not completely burden-free. Adverse events, such as skin reactions, were more common in the CGM group, so patient education and support remain important.
• This study found no clear benefit to women planning pregnancy due to small sample size. Therefore, larger studies are needed in women who are planning pregnancy to detect potential benefits of CGMs..
•The authors noted a lack of data regarding capillary glucose testing frequency, its impact on glycemic control, and the prevalence of insulin suspension. Furthermore, they observed an increase in unscheduled clinical contacts within the CGM group. Future studies need to investigate the requisite levels of patient support and identify the specific clinical drivers underpinning these observed benefits.
BACKGROUND
Pregnant women with type 1 diabetes are a high-risk population who are recommended to strive for optimal glucose control, but neonatal outcomes attributed to maternal hyperglycaemia remain suboptimal. Our aim was to examine the effectiveness of continuous glucose monitoring (CGM) on maternal glucose control and obstetric and neonatal health outcomes.
METHODS
In this multicentre, open-label, randomised controlled trial, we recruited women aged 18-40 years with type 1 diabetes for a minimum of 12 months who were receiving intensive insulin therapy. Participants were pregnant (≤13 weeks and 6 days' gestation) or planning pregnancy from 31 hospitals in Canada, England, Scotland, Spain, Italy, Ireland, and the USA. We ran two trials in parallel for pregnant participants and for participants planning pregnancy. In both trials, participants were randomly assigned to either CGM in addition to capillary glucose monitoring or capillary glucose monitoring alone. Randomisation was stratified by insulin delivery (pump or injections) and baseline glycated haemoglobin (HbA). The primary outcome was change in HbA from randomisation to 34 weeks' gestation in pregnant women and to 24 weeks or conception in women planning pregnancy, and was assessed in all randomised participants with baseline assessments. Secondary outcomes included obstetric and neonatal health outcomes, assessed with all available data without imputation. This trial is registered with ClinicalTrials.gov, number NCT01788527.
FINDINGS
Between March 25, 2013, and March 22, 2016, we randomly assigned 325 women (215 pregnant, 110 planning pregnancy) to capillary glucose monitoring with CGM (108 pregnant and 53 planning pregnancy) or without (107 pregnant and 57 planning pregnancy). We found a small difference in HbA in pregnant women using CGM (mean difference -0·19%; 95% CI -0·34 to -0·03; p=0·0207). Pregnant CGM users spent more time in target (68% vs 61%; p=0·0034) and less time hyperglycaemic (27% vs 32%; p=0·0279) than did pregnant control participants, with comparable severe hypoglycaemia episodes (18 CGM and 21 control) and time spent hypoglycaemic (3% vs 4%; p=0·10). Neonatal health outcomes were significantly improved, with lower incidence of large for gestational age (odds ratio 0·51, 95% CI 0·28 to 0·90; p=0·0210), fewer neonatal intensive care admissions lasting more than 24 h (0·48; 0·26 to 0·86; p=0·0157), fewer incidences of neonatal hypoglycaemia (0·45; 0·22 to 0·89; p=0·0250), and 1-day shorter length of hospital stay (p=0·0091). We found no apparent benefit of CGM in women planning pregnancy. Adverse events occurred in 51 (48%) of CGM participants and 43 (40%) of control participants in the pregnancy trial, and in 12 (27%) of CGM participants and 21 (37%) of control participants in the planning pregnancy trial. Serious adverse events occurred in 13 (6%) participants in the pregnancy trial (eight [7%] CGM, five [5%] control) and in three (3%) participants in the planning pregnancy trial (two [4%] CGM and one [2%] control). The most common adverse events were skin reactions occurring in 49 (48%) of 103 CGM participants and eight (8%) of 104 control participants during pregnancy and in 23 (44%) of 52 CGM participants and five (9%) of 57 control participants in the planning pregnancy trial. The most common serious adverse events were gastrointestinal (nausea and vomiting in four participants during pregnancy and three participants planning pregnancy).
INTERPRETATION
Use of CGM during pregnancy in patients with type 1 diabetes is associated with improved neonatal outcomes, which are likely to be attributed to reduced exposure to maternal hyperglycaemia. CGM should be offered to all pregnant women with type 1 diabetes using intensive insulin therapy. This study is the first to indicate potential for improvements in non-glycaemic health outcomes from CGM use.
FUNDING
Juvenile Diabetes Research Foundation, Canadian Clinical Trials Network, and National Institute for Health Research.
Copyright © 2017 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.
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