Study examined effectiveness of CGM on maternal glucose control and obstetric and neonatal health outcomes.
Pregnant women with type 1 diabetes are a high-risk population who are recommended to strive for optimal glucose control, but neonatal outcomes attributed to maternal hyperglycemia remain suboptimal.
Use of a CGM device that provides 288 glucose recordings per day allows women to rapidly respond to changes in blood glucose levels; by comparison, the so-called finger-prick method of glucose monitoring is carried out four to eight times a day, on average.
Studies in adults with type 1 diabetes have shown reduction in HbA1c and exposure time to hypoglycemia when using CGM, “but very few data exist in pregnant women,” said Dr. Denice Feig, explaining the motivation for the study. With this in mind, the aim of CONCEPTT was to assess the effectiveness of CGM on glycemic control in women with type 1 diabetes who were pregnant or planning pregnancy.
The researchers ran two trials in parallel for pregnant participants (n = 215) and for participants planning pregnancy (n = 110). In both trials, participants were randomly assigned to either CGM in addition to capillary glucose monitoring or capillary glucose monitoring alone. The primary outcome was change in HbA1c from randomization to 34 weeks’ gestation in pregnant women and to 24 weeks or conception in women planning pregnancy.
Results presented here focused on the group who were already pregnant.
The multinational, open-label study was carried out across 31 hospitals in Canada, England, Ireland, Italy, Scotland, Spain, and the United States. Women managed their diabetes with insulin pumps (n = 108) or MDI (n = 107), but had suboptimal control (HbA1c 6.5–10% in pregnancy; they had to be in their first trimester of a singleton pregnancy).
Half were randomly allocated to use the CGM device, and half to use the traditional fingerstick blood glucose monitoring method. The CGM was worn for approximately 24 weeks (from 10–12 weeks until the end of their pregnancy).
Women were taught how to use CGM, how to change their insulin, and how to take a capillary glucose (fingerprick) test. Study visits were every 4 weeks (weeks 12 to 36). Women in the control group did at least seven fingerstick tests a day.
Dr. Helen Murphy presented the results of the intention-to-treat analysis. The primary outcome was change in HbA1c from randomization to 34 weeks’ gestation in pregnant women, with the sample size calculation intended to detect a between-group difference of 0.5%, and they found a small difference in HbA1c in pregnant women using CGM, mean difference −0.19%, vs those in the control group using fingerprick tests (P = .0207), but this meant the primary end point wasn’t technically met. CGM users spent more time in the target HbA1c range (68% vs 61% of controls, P = .0034); and less time in hyperglycemia (>7.8 mmol/L) (27% vs 32%, P = .0279). But severe hypoglycemia episodes were comparable between the two groups (18 among CGM users and 21 in controls) as was time spent in hypoglycemia (3% vs 4%, P = .10). And in terms of frustration, 80.6% in the CGM arm compared with 12.5% in the fingerprick group encountered problems (eg, sensor not inserted properly). There was no improvements in severe hypoglycemia in this high-risk population. The odds ratios of having the main neonatal events were reduced by approximately 50% between groups. One needed to treat only six women with CGM to prevent one episode of large-for-gestational-age, eight women to prevent one event of neonatal hypoglycemia, and six to prevent an NICU admission of over 24 hours.
In conclusion, use of CGM during pregnancy in patients with type 1 diabetes is associated with improved neonatal outcomes, which are likely to be attributed to reduced exposure to maternal hyperglycemia. CGM should be offered to all pregnant women with type 1 diabetes using intensive insulin therapy. This study is the first to indicate potential for improvements in non-glycemic health outcomes from CGM use.
- There were no improvements in severe hypoglycemia.
- The primary endpoint of improving A1c was not technically met.
- Use of CGM during pregnancy in patients with type 1 diabetes is associated with improved neonatal outcomes.