CGM Influences Hyperglycemia Risk for Pregnant Women with T1D


Continuous glucose monitoring was shown to lower the risk of hyperglycemia compared to capillary glucose monitoring alone.

Denise S. Feig, MD, MSc

Denise S. Feig, MD, MSc

Results of a study published in The Lancet in September indicate that using continuous glucose monitoring (CGM) during pregnancy may improve neonatal outcomes and also reduce the maternal risk for hyperglycemia in pregnant women with type 1 diabetes (T1D).

Combined with T1D, pregnancy can put women at high risk for hyperglycemia, with resulting suboptimal neonatal outcomes.

Led by Denise S. Feig, MD, MSc, an associate professor at the University of Toronto’s Institute of Health Policy, Management, and Evaluation, the investigators looked at CGM’s effects on glucose control in mothers, as well as obstetric and neonatal outcomes. The multicenter, open-label, randomized controlled trial randomly assigned 2 groups of women aged 18 to 40 years to either CGM and capillary glucose monitoring, or capillary glucose monitoring alone.

The CGM-treated group was made up of 325 women (215 pregnant, 110 who were planning pregnancy), while the group treated with capillary glucose monitoring alone consisted of 107 pregnant women, and 57 planning a pregnancy. Pregnant participants were all 13 weeks pregnant or less and at least 6 days gestation.

Patients were randomized based on their insulin delivery (pump or injection) and baseline glycated hemoglobin (HbA1c). The study’s primary outcome was a change in HbA1c from baseline to 34 weeks in pregnant participants, and 24 weeks or conception in the women planning a pregnancy. Among the secondary outcomes were obstetric and neonatal health outcomes.

The pregnant women using CGM experienced a small difference in HbA1c (mean difference −0·19%; 95% CI −0.34 to −0.03; P = .0207). They also experienced less hyperglycemia than pregnant control participants (27% vs 32%; P = .0279). The incidence of hypoglycemia was comparable between both groups.

Researchers said neonatal outcomes showed significant improvements, including fewer neonatal ICU admissions that lasted more than 24 hours, as well as an average of 1 day shorter length of hospital stays, less neonatal hypoglycemia, and lower incidence of large for gestational age.

The study team reportedly found “no apparent benefit” for CGM in participants who had been planning a pregnancy.

In a supplementary commentary, Satish K. Garg, MD, and Sarit Polsky, MD, both from The Barbara Davis Center for Diabetes at the University of Colorado Denver, said, “We believe the 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.”

However, Garg and Polsky also caution that “the biggest drawback in the study” was a lack of information about self-monitoring frequency and its association to HbA1c improvements for the control group.

“Studies from different registries have reported that the frequency of self-monitoring of blood glucose is associated with HbA1c levels,” Garg and Polsky said. “However, all women in the trial were required to obtain at least 4 capillary glucose tests daily to be eligible, and were advised to test levels at least 7 times a day; pregnant women with diabetes typically perform 7 to 10 tests per day. Furthermore, a cost-benefit analysis from this study needs to justify use of CGM during pregnancy compared with self-monitoring alone.”

The editorial concluded that the use of pumps with CGM does, in fact, reduce hypoglycemia, especially at night, when it is a major concern for the high-risk population. “Future studies need to evaluate the now approved hybrid closed-loop system during pregnancies associated with type 1 diabetes, as well as new artificial pancreas systems that might reach the market,” Garg and Polsky concluded.

The study ran from March 25, 2013, to March 22, 2016, and the women were observed in hospitals in the U.S., Canada, England, Scotland, Spain, Italy, and Ireland.

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