Spotlight on technology for pregnant diabetes patients

Several recent studies looked at the use of continuous glucose monitoring (CGM) and automated insulin pumps in pregnant patients with pre-existing diabetes.

A study published by Diabetes Care on Oct. 2 looked retrospectively at a cohort study of 117 patients with type 1 or 2 diabetes who used real-time CGM during pregnancy (58.1% with type 1 diabetes). Overall, 83.8% experienced the primary outcome, a composite of fetal or neonatal mortality, large or small for gestational age at birth, neonatal ICU admission, hypoglycemia, shoulder dystocia or birth trauma, and hyperbilirubinemia. The study found that all CGM metrics, except time below 65 mg/dL (3.6 mmol/L), were associated with neonatal morbidity. For each 5-percentage-point increase in time within the target range (TIR) of 65 to 140 mg/dL (3.6 to 7.8 mmol/L), there was a 28% reduction in odds of neonatal morbidity. The statistically optimal TIR was 66% to 71%, according to the study. The authors observed that the findings support the American Diabetes Association recommendation of 70% TIR and called for additional research in this area to help improve the utility of CGM during pregnancy.

A similar study, published by Diabetes, Obesity and Metabolism on Sept. 21, involved a post hoc analysis of a trial that randomized some pregnant patients on insulin to CGM (50 patients with type 1 diabetes and 94 with either type 2 or gestational diabetes). Researchers found that, in patients with type 1, a higher mean glucose level in the second trimester was associated with a large-for-gestational-age (LGA) baby (odds ratio, 2.6; 95% CI, 1.1 to 6.2). In type 2 and gestational diabetes, time above the target range (as measured by area under the curve) was associated with LGA. However, none of the CGM metrics were associated with neonatal hypoglycemia, pre-eclampsia, shoulder dystocia, preterm birth, or neonatal ICU admission. The study authors noted that the pregnant patients were not given real-time CGM data in the study, which might have limited the effects of the technology, but they said that the findings “can provide clinicians with guidance on the utility of CGM metrics … as sensor technology has seen rapid uptake largely driven by the availability and consumer friendly nature compared with SMBG [self-monitored blood glucose], rather than strong evidence.”

Two other studies looked at adding automated insulin delivery to CGM. One, published by the Journal of Diabetes Investigation on Sept. 14, looked retrospectively at 69 pregnancies in type 1 diabetes patients: 40 treated with CGM and a sensor-augmented insulin pump and 29 treated with continuous subcutaneous insulin infusion plus SMBG. The group using CGM plus the automated pump had lower peripartum HbA1c levels (6.1% vs. 6.5%; P<0.05) and much lower incidence of LGA (27.5% vs. 65.5%; P<0.05). There were no significant differences in hypertensive disorders, small for gestational age, respiratory distress syndrome, neonatal hypoglycemia, hypervolemia, or hyperbilirubinemia. The study authors concluded that sensor-augmented insulin pumps “might be effective in preventing the incidence of LGA in pregnant women with type 1 diabetes,” noting that they believe this to be the first study showing its superiority to continuous subcutaneous insulin plus SMBG.

The other study, published Oct. 5 by the New England Journal of Medicine, was a randomized trial in 124 pregnant women with type 1 diabetes. All were on CGM, and half received standard insulin therapy while the other half were put on hybrid closed-loop therapy. The latter group spent a higher percentage of time in the target range of 63 to 140 mg/dL (3.5 to 7.8 mmol/L): 68.2% versus 55.6% (mean adjusted difference, 10.5 percentage points [95% CI, 7.0 to 14.0 percentage points]; P<0.001). No unanticipated safety problems with the closed-loop therapy were identified (6 instances of severe hypoglycemia vs. 5 with standard care, 1 case of diabetic ketoacidosis in each group, 12 device-related adverse events in the closed-loop group). “Our trial was not powered for pregnancy outcomes, but we infer that this additional 10 percentage points of time in the pregnancy-specific target range would be expected to have additional health benefits for pregnant persons and their babies,” said the study authors, who added that “hybrid closed-loop therapy should be offered to all pregnant persons with type 1 diabetes.” An accompanying editorial said, “The importance of these findings cannot be understated” but noted a number of barriers to wider use of the technology, “including biases related to socioeconomic status, ethnicity, and implicit racial bias.”