A multinational randomized controlled trial indicates, for what may be the first time, that continuous glucose monitoring (CGM) may have health benefits that go well beyond control of maternal hyperglycemia. The results, published in The Lancet, were generalizable across the 31 international study sites.
Researchers from Canada, England, Scotland, Spain, Italy, Ireland and the United States ran 2 parallel trials—one with pregnant women and one with women who were planning a pregnancy—all of whom had type 1 diabetes for at least 12 months. The 325 participants were receiving intensive insulin therapy and were randomly assigned to either CGM in addition to capillary glucose monitoring or capillary glucose monitoring alone. Randomization was stratified by insulin delivery (pump or injections) and baselined glycated hemoglobin (HbA1c).
The primary outcome was change in HbA1c from randomization to 34 weeks’ gestation in pregnant women and to 24 weeks or conception in the women planning pregnancy. Obstetric and neonatal health outcomes were the secondary outcomes.
CGM was associated with a small difference in HbA1c in pregnant women (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 = 00034) and less time hyperglycemic (27% vs 32%; P = 0.0279) than did pregnant controls, with comparable severe hypoglycemia episodes and time spent hypoglycemic.
More importantly, CGM significantly improved neonatal health outcomes, with lower incidence of large-for-gestational-age (LGA) (odds ratio 0.51, 95% CI 0.28 to 0.90; P = 0.0210), fewer neonatal intensive care unit (NICU) admissions lasting longer than 24 hours (0.48; 0.26 to 0.86; P = 0.0157), fewer incidents of neonatal hypoglycemia (0.45; 0.22 to 0.89; P = 0.0250) and a 1-day shorter length of hospital stay (P = 0.0091). No benefit was found for 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.
The number of pregnant women needed to treat with CGM to prevent 1 newborn complication, the authors said, is 6 for both NICU admission and LGA and 8 for neonatal hypoglycemia. They concluded that “national and international guideline recommendations in type 1 diabetes in pregnancy should be revised to recommend offering CGM to pregnant women with type 1 diabetes using intensive insulin therapy in the first trimester.”