Achieving American Diabetes Association (ADA) HbA1c targets during pregnancy has been found to be associated with better perinatal outcomes in women with type 1 diabetes (T1D), according to research results published in Diabetes Technology & Therapeutics.

Researchers performed a secondary subanalysis of data from CONCEPTT ( Identifier: NCT01788527), a randomized controlled trial including 215 pregnant women and 110 women planning to become pregnant, in order to evaluate continuous glucose monitor (CGM)-based and ADA HbA1c target glucose achievement. The secondary goal was to evaluate the relationship between CGM and HbA1c target achievements with pregnancy outcomes.

In the current study, the researchers obtained CGM measurements and blood samples per the CONCEPTT study protocol. Six-day CGM readings and HbA1c measurements were analyzed in the first trimester and again at 24 and 34 weeks’ gestation. The primary study outcome was the percentage of women who achieved the target CGM and target HbA1c at all 3 time points.

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The cohort included 221 women at baseline, 197 women at 24 weeks, and 172 women at 34 weeks. Mean participant age was 31.5 years, mean BMI was 25.8 kg/m2, duration of T1D was 16.8 years, and gestational age at randomization or pregnancy confirmation was 10.2 weeks. Mean baseline HbA1c was 6.9%.

The investigators found that the rate of achieving the HbA1c target increased during pregnancy. At week 34, the percentage of women who achieved time in range, time above range, and time below range targets was higher in the real-time CGM group compared with those in the control group.

At baseline, 53.8% of women did not meet any of the CGM targets; this number decreased to 32% at week 24 and 5.8% at week 34. Simultaneous attainment of the 3 CGM targets took place in 2.7%, 2.0%, and 17.0% of the study participants, respectively.

Throughout the study, the percentage of women with HbA1c less than 6.5% and less than 6% increased during pregnancy, although the proportion of women who achieved period-specific goals did not change. Both groups differed at week 34 in the frequency of HbA1c target achievement — 31% vs 17% — due to a “nonsignificant increase in the real-time CGM group and a nonsignificant decrease in the control group.”

Overall, 13.1% of the participants experienced preeclampsia, 67% had a cesarean section, 40.3% had preterm birth, and 61.3% had infants born large for gestational age; 24.5% of the infants had neonatal hypoglycemia, and 37.3% required care in the neonatal intensive care unit (NICU).

Achieving target time in range at 34 weeks was associated with lower risk of preterm birth, while achieving target time above range at 24 weeks was associated with a lower risk of infants being large for gestational age. Achieving target time below range at 24 weeks was associated with an increased risk of neonatal hypoglycemia and NICU stay.

In terms of HbA1c-specific risks, achieving HbA1c less than 6.5% in the first trimester was associated with a lower risk of infants born large for gestational age, while HbA1c less than 6% at 24 weeks was associated with a lower risk of preterm birth, infants born large for gestational age, neonatal hypoglycemia, and NICU stay.

After adjusting for clinical variables, achievement of target time below range in the first trimester was associated with increased risk of preeclampsia and neonatal hypoglycemia at 24 weeks. For HbA1c, achieving the ADA trimester-specific target in the first trimester was associated with reduced risk of infants born large for gestational age, preterm birth, and neonatal hypoglycemia at 24 weeks.

Study limitations included the analysis of only 6-day CGM readings and the exclusion of women with first-pregnancy HbA1c less than 6.5% or greater than 10% at enrollment.

The study authors reported that “CONCEPTT trial participants had a low rate of CGM and HbA1c target attainment especially for the trimester-specific ADA HbA1c targets, which were unchanged during pregnancy.”

“Attainment of CGM and [National Institute for Health and Care Excellence] HbA1c targets increased throughout gestation and all targets…were more likely to be achieved by RT-CGM users at 34 weeks’ gestation,” they added.

“ADA HbA1c target achievement was independently associated with better prenatal outcomes while the independent association of [time below range] target achievement with increased risk warrants further study,” the study authors concluded.


Tundidor D, Meek CL, Yamamoto J, et al; CONCEPTT Collaborative Group. Continuous glucose monitoring time-in-range and HbA1c targets in pregnant women with type 1 diabetes. Diabetes Technol Ther. Published online May 25, 2021. doi:10.1089/dia.2021.0073