Conference Coverage

Endocrinologists clash over routine CGM during pregnancy



– Diabetes and pregnancy aren’t a good mix, but what about pregnancy and continuous glucose monitors (CGMs)? In a polite but pointed debate, two endocrinologists used each other’s studies as evidence to support their opposing perspectives about routine GCM use by diabetic women during pregnancy.

Dr. Denise Feig University of Toronto

Dr. Denise Feig

“This topic shouldn’t really be debated because the evidence is clear” in favor of CGM, said Denice S. Feig, MD, MSc, FRCPC, of the University of Toronto and Mt. Sinai Hospital, also in Toronto, in a presentation at the annual scientific sessions of the American Diabetes Association.

However, Elisabeth R. Mathiesen, MD, DMSc, of Rigshospitalet in Copenhagen, rebutted. She said her own research suggests CGM use may lead to larger babies and more premature births, convincing her to “say no to uncritical use of CGM in pregnancy.”

At issue: What is the best routine treatment for diabetic women before, during, and after pregnancy? As the American Diabetes Association noted in its 2018 Standards of Medical Care in Diabetes report, “specific risks of uncontrolled diabetes in pregnancy include spontaneous abortion, fetal anomalies, preeclampsia, fetal demise, macrosomia, neonatal hypoglycemia, and neonatal hyperbilirubinemia, among others. In addition, diabetes in pregnancy may increase the risk of obesity and type 2 diabetes [mellitus] in offspring later in life.”

In her presentation, Dr. Feig pointed to a 2017 study she led that examined the effectiveness of continuous, real-time CGM on women with type 1 diabetes mellitus who were pregnant or planning to become pregnant (Lancet. 2017 Nov 25;390(10110):2347-2359).

“The study, in effect, was two parallel, randomized trials, one in those who planned pregnancy and one in those who were pregnant,” Dr. Feig said.

Participants, aged 18-40 years, from 31 hospitals in seven European and North American nations, had to have hemoglobin A1c levels greater than or equal to 6.5% during pregnancy or greater than or equal to 7% while planning pregnancy to be included in the study.

“We had a run-in phase to make sure they were able and willing to wear the CGM. Then we had 215 women in the pregnancy arm and 110 in the prepregnancy group randomized to real-time continuous CGM or standard care,” Dr. Feig said. The study ran for 34 weeks in the pregnant patients and for 24 weeks or until conception in the other women.

According to Dr. Feig, 70% of pregnant participants used CGM devices for more than 75% of the time. Compared with the control group, HbA1c levels in those who used CGM fell by 0.19% (P = .0207). The researchers also reported that women in the CGM group spent 100 more minutes a day within the glucose target range.

No differences in outcomes such as gestational age at delivery and rate of preterm delivery was found, although incidence of large-for-gestational-age infants, hypoglycemia requiring dextrose infusion, and neonatal ICU admission were lower in the CGM group to a statistically significant degree. “The numbers needed to treat were very small at six to eight women to reduce one of these events,” said Dr. Feig, who added that the numbers suggest the potential for cost savings.

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