T1DM, Pregnancy, and Continuous Glucose Monitoring: Good News


A new open-label randomized controlled trial finds use of CGM in T1DM pregnancies may improve neonatal outcomes.

Currently there are only a handful of small retrospective studies that have looked at continuous glucose monitoring (CGM) in women with type 1 diabetes who are pregnant. Contrary to results of those studies--little or no improvement was seen in maternal or fetal outcomes--the Continuous Glucose Monitoring in Pregnant Women with Type 1 Diabetes (CONCEPTT) trial suggests that CGM may improve outcomes other than glycemia and may also improve neonatal outcomes. Following is a summary of the study and its results. 

T1D and Pregnancy: A Risky Combination

● T1D increases the risk for pre-eclampsia, caesarian, congenital anomalies, preterm birth, perinatal mortality, large for gestational age (LGA), need for neonatal intensive care unit (NICU)
● Optimal glycemic control early in pregnancy may improve maternal and fetal outcomes
     o Challenges include complexity of insulin dosing, pregnancy-related changes in insulin sensitivity and insulin absorption

Can CGMs improve Maternal and Fetal Outcomes in T1D?

● In January 2017, CMS authorized payment for CGM in insulin-dependent diabetes
● ADA, EASD, ACOG, AACE have not specifically recommend CGMs in pregnant women with T1D
● So far, only small, retrospective studies have evaluated CGM in pregnant women with T1D
     o Results suggest little or no improvement in maternal and fetal outcomes


● First trial to suggest CGMs may improve outcomes other than glycemia, and may improve neonatal outcomes
● Open-label RCT of 325 women aged 18-40 with T1D
     o In 31 hospitals in Canada, England, Scotland, Spain, Italy, Ireland, USA
     o Parallel trials for pregnant women (n=215) and women planning pregnancy (n=110)
     o Randomized to CGM plus fingersticks (288 readings/day) or fingersticks alone (controls, 4-8 times/day)
● Primary outcome: change in HbA1c from randomization (<14 weeks’ gestation) to 34 weeks’ gestation in pregnant women or 24 weeks in women planning pregnancy
     o CGM worn for about 24 weeks in both groups

CGMs in Pregnant Users Linked to Better Glucose Control

● Glucose control in pregnant women:
     o HbA1c: Small improvement with CGM vs controls (mean difference −0.19%; 95% CI −0.34 to −0.03; p=0.0207)
     o Time in target: About 100 minutes longer per day with CGM (68%) vs controls (68% vs 61%; p=0.0034)
     o Time in hyperglycemia: About 1 hr less per day with CGM vs controls (27% vs 32%; p=0.0279)
     o Glucose variability: Lower with CGM vs controls (p<0.0001- 0.058)
● No significant differences in severe hypoglycemia, time spent in hypoglycemia, weight gain, pre-eclampsia, caesarean, preterm births, maternal length of stay
● Women planning pregnancy: No apparent benefit for CGMs

CGMs Linked to Improved Neonatal Outcomes

● LGA: 49% lower odds with CGM vs control (OR 0.51, 95% CI 0.28 to 0.90; p=0.0210)
● NICU admission over 24 hrs: 52% lower odds with CGM vs controls (OR 0.48; 0.26 to 0.86; p=0.0157)
● Neonatal hypoglycemia: 55% lower odds with CGM vs controls (OR 0.45; 0.22 to 0.89; p=0.0250)
● Hospital stay: One day shorter with CGM vs controls (p=0.0091)
● Number of pregnant women needed to treat with CGM:
     o 6 to prevent one newborn complication
     o 6 prevent one NICU admission
     o 8 to prevent one neonatal hypoglycemia episode

Safety and Tolerability

● Numbers of adverse events and serious adverse events similar for CGM vs controls (p=0.041 and p=0.82, respectively)
● Most common adverse events: skin reactions in 44-48% of CGM users and 8-9% of controls
● 80% of CGM users voiced frustrations about the device

Study Limitations

● Did not meet primary endpoint of 0.5% between-group difference in HbA1c
● About 20% of HbA1c measurements were missing
● CGM group had more scheduled and unscheduled visits with providers, which could have contributed to the results
● Neonatal outcomes still suboptimal:  53-69% of babies were born LGA
● Cost-benefit analyses needed

Expert commentary on outcomes: “We believe that the CONCEPTT results support CGM use during pregnancy for all women with type 1 diabetes and time in range might become an important measure in pregnancies associated with type 1 diabetes; thus endocrine and obstetric medical societies could consider advocating or recommending revising their guidelines accordingly.” Satish Garg, MD, and Sarit Polsky, MD, The Barbara Davis Center for Diabetes, University of Colorado Denver (Aurora, CO)


1. 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 Sep 15. pii: S0140-6736(17)32400-5. doi: 10.1016/S0140-6736(17)32400-5.
2. Garg SK, Polsky S. Continuous glucose monitoring in pregnant women with type 1 diabetes. Lancet. 2017 Sep 15. doi: 10.1016/S0140-6736(17)32449-2

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