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In Pregnant Women with T1D, Greater Time in Range Reduces Adverse Maternal, Neonatal Outcomes


Higher time in optimal glycemic range was associated with reduced risk for preeclampsia and for birth weight larger than gestational age, new research found.

A recent study of women with type 1 diabetes (T1D) who were pregnant found that each 5-unit increase in time spent in optimal glycemic range at as early as 12 weeks of gestational age was associated with a nearly 50% reduction in risk for preeclampsia and of delivering an infant larger than gestational age (LGA).

Time in range (TIR) in the study was based on use of continuous glucose monitoring (CGM), the glucose tracking strategy becoming more common among women with T1D who are pregnant, according to the study authors. More widespread use of CGM in this population has also increased interest in the potential associations between pregnancy outcomes and CGM parameters, and particularly TIR, the investigators wrote in the American Journal of Obstetrics and Gynecology.

“In 2019, an international expert consensus suggested a goal time in range of above 70% throughout pregnancy for patients with type 1 diabetes. However, this recommendation was not based on robust data relating specific time in range thresholds to clinically relevant perinatal outcomes,” Nasim C Sobhani, MD, MAS, assistant professor in the division of maternal-fetal medicine in the department of obstetrics, gynecology and reproductive sciences at the University of California, San Francisco, and colleagues wrote. Moreover, the current study findings that fewer than 30% of participants reached the ideal of 70% or greater TIR at each of the gestational ages (GA) evaluated strongly suggests that “this benchmark is challenging to achieve.”

Sobhani and colleagues conducted a multicenter retrospective cohort study with data from 91 pregnant women with type 1 diabetes using continuous glucose monitors who delivered from 2020 to 2022 at 5 University of California Fetal Consortium sites.

All women had a continuous glucose monitor target range of 70 mg/dL to 140 mg/dL. Researchers recorded time in range at 12, 16, 20, 24, 28 and 32 weeks.

The primary maternal outcome was preeclampsia, and the primary neonatal outcome was LGA.

Mean age of the participants was 32.6 years. Approximately two-thirds (67%) identified as nonHispanic White and 14% as Hispanic. The median periconception HbA1c was 6.7% (range 5.8 – 7.6%). In the cohort, 81% of women used an insulin pump and 72% did not have diabetes-related microvascular disease. Median time since type 1 diabetes diagnosis was 16 years.


Overall, 29% of women developed preeclampsia. Compared with these women, participants who were normotensive had higher time in range (from 56% to 62% vs 43% to 50%) at nearly all time GA time points.

Twenty-six percent of women had infants assessed as LGA. As observed for the preeclampsia outcomes, TIR was higher, from 55% to 64%, among women with normal birth weight infants compared with TIR for women with LGA infants, from 41% to 47%.

In Pregnant Women with T1D, Greater Time in Range Reduces Adverse Maternal, Neonatal Outcomes

Sobhani et al reported that at as early as 12 weeks gestation, every 5-unit increase in TIR was associated with a 45% reduced risk for preeclampsia (adjusted RR = 0.55; 95% CI, 0.3-0.99) and with a 46% reduced risk for LGA infants (aRR = 0.54; 95% CI, 0.29-0.99) in adjusted analyses.

“These findings provide important preliminary data that can guide detailed patient counseling in the clinical setting. Rather than dichotomizing TIR as above or below a certain benchmark, practitioners can provide patients with nuanced information regarding predicted likelihood of outcome based on their current TIR,” wrote authors when discussing clinical implications of the findings. Sobhani and colleagues said that even more importantly, “the health care team can provide reassurance that even small improvements in TIR can have an appreciable effect on clinical outcomes.”

Source: Sobhani NC, Goermans S, Nguyen A, et al. Continuous glucose monitoring in pregnancies with type 1 diabetes: small increases in time-in-range improve maternal and perinatal outcomes. Am J Obstet Gynecol. Published online January 16, 2024. doi:10.1016/j.ajog.2024.01.010

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