Women with type 1 diabetes reach CGM targets later in pregna
Pregnant women with type 1 diabetes using a continuous glucose monitor improved their time in range from their first trimester to 34 weeks of pregnancy, according to study data.

In subanalysis data from the CONCEPTT randomized trials, more than half of pregnant women with type 1 diabetes assigned to use real-time CGM did not reach their target of more than 70% of time in range with a glucose level between 3.5 mmol/L and 7.8 mmol/L during their first trimester. The percentage of women reaching their time-in-range goal in the CGM group progressively improved during pregnancy.

Researchers extracted data from 215 women who were enrolled in the CONCEPTT pregnancy trial and 34 women in the planning pregnancy trial who later became pregnant (mean age, 31.5 years). In CONCEPTT, participants were randomly assigned to a group using real-time CGM plus capillary glucose monitoring or a control group using capillary glucose monitoring alone. Baseline 6-day CGM readings and HbA1c measurements were collected during the first trimester, and follow-up readings and measurements were collected at 24 and 34 weeks of gestation.

Data on incidences of preeclampsia, cesarean section, preterm birth, large for gestational age, neonatal hypoglycemia and neonatal ICU admission were collected also. Researchers also measured the percentage of women with an HbA1c less than 6.5% in the first trimester and less than 6% in the second and third trimesters as recommended by the ADA.

Improved time in range later in pregnancy

There were 221 participants with real-time CGM data available at baseline, 197 included in the analysis at 24 weeks, and 172 women included in the 34-week analysis. At baseline, 53.8% of women did not meet any of the time-in-range, time-above-range and time-below-range targets. That proportion decreased to 32% at 24 weeks and 5.8% at 34 weeks.

The percentage of women meeting ADA-specified HbA1c goals increased during pregnancy, but the proportion did not significantly change. At 34 weeks, more women in the CGM group reached their HbA1c target compared with the control cohort (31% vs. 17%).

“These results suggest that, even when real-time CGM has been shown to improve clinical outcomes, additional improvement is required for women to reach the tight CGM time-in-range and ADA HbA1c targets before late gestation,” the researchers wrote. “Possible solutions may include better prepregnancy planning, lifestyle changes, as well as treatment and technological advances.”

Time below range linked to pregnancy risks

Of the study cohort, 13.1% had preeclampsia, 67% cesarean section, 40.3% preterm birth, 61.3% large for gestational age, 24.5% neonatal hypoglycemia and 37.3% neonatal ICU admission. After adjusting for clinical variables, women who attained their time-below-range target at baseline had an increased risk for preeclampsia and a higher risk for neonatal hypoglycemia at 24 weeks.

“This suggests that either the time below range cutoff of 3.5 mmol/L is too high and/or that the 4% of time (1 hour per day) used to define the target is too low,” researchers said.

Participants who attained the ADA trimester-specific HbA1c target in their first trimester had a lower risk for large at gestational age, a lower risk for preterm birth and neonatal hypoglycemia at 24 weeks, and a reduced risk for preterm birth at 34 weeks.

Researchers said future research should reassess time below range, time in range and time above range targets using glucose sensors with improved accuracy. Studies examining new methods of glucose monitoring, new insulin analogs and hybrid closed-loop systems should also be performed.

Source: https://www.liebertpub.com/doi/10.1089/dia.2021.0073