CGM Can Help Pregnant Patients With T1D Improve TIR, Outcomes


Despite previously suggested benchmarks, investigators found that spending less time-in-range (TIR) can still improve maternal and perinatal outcomes among pregnant patients with type 1 diabetes (T1D).

New research found that a 5-unit increase in time-in-range (TIR) measured by continuous glucose monitoring (CGM) at 12 weeks among pregnant patients with type 1 diabetes (T1D) was associated with an almost 50% decreased risk of adverse pregnancy outcomes, including developing preeclampsia and delivering a large-for-gestational-age (LAG) infant. Findings were published in the American Journal of Obstetrics and Gynecology.1

Pregnant woman using continuous glucose monitor / Andrey Popov -

Pregnant woman using continuous glucose monitor / Andrey Popov -

Investigators noted that just a 5% increase in the amount of time pregnant patients with T1D spent in range resulted in improved clinical outcomes, underscoring the benefits of even modest progress in management of the condition.

Key Takeaways

  • Spending just 5% more TIR led to improved maternal and perinatal outcomes among pregnant patients with T1D, underlining the benefits of even modest improvement and the importance of CGMs in monitoring precise glucose levels.
  • Less than 30% of the patient population achieved a TIR of above 70% throughout the study, suggesting that the previously suggested benchmark might be difficult to accomplish in practice.
  • Small improvements in TIR might not only lead to improved patient outcomes, but also help alleviate emotional and administrative burdens associated with managing T1D among pregnant patients.

Although experts have previously suggested that pregnant patients with T1D should maintain a TIR of above 70% throughout pregnancy to ensure positive outcomes, this metric has not been supported by clinical data. To supplement this lack of literature, investigators examined the association between TIR at different gestational ages and risk of perinatal and maternal complications among the patient population.

Investigators recruited participants across 5 academic tertiary centers within the University of California (UC) Fetal Consortium—UC Davis, UC Irvine, UC Los Angeles, UC San Diego, and UC San Francisco—who had T1D, used a CGM, and delivered between 2020 to 2022.

TIR data, elicited by CGMs, was recorded at 12, 16, 20, 24, 28, and 32 weeks for each of the 91 patients included. Whereas patients have traditionally used at-home glucometers and laboratory testing of hemoglobin A1c to monitor blood glucose levels, CGMs, which provide automatic and rich glycemic information to the user, have begun to supplement and replace them.

The primary maternal outcome was preeclampsia and the primary neonatal outcome was LGA, defined as having a birthweight that measured in the 95th percentile for gestational age or higher.

About 29% of the study population developed preeclampsia, spending less TIR compared to those without preeclampsia at every time point. Across gestation, patients who developed preeclampsia had a TIR that ranged between 43-50% and patients who remained normotensive ranged between 56-62%.

READ MORE: Slideshow: The Role of CGM in Diabetes Management During Pregnancy

Further, 26% of participants gave birth to an LGA infant. At every recorded time point, these participants spent less TIR than participants who delivered normal weight infants, ranging from 41-47% and 55-64% across gestation, respectively.

Perhaps most notably, investigators found that every 5-unit increase in TIR at 12 weeks was linked to a 46% decreased risk of delivering a LGA infant and a 45% decreased risk of developing preeclampsia. Each 5% improvement in TIR at 12 weeks corresponded to only 1.2 extra hours per day spent in range, demonstrating how even small thresholds of improvement are clinically impactful.

Overall, less than 30% of the patient population maintained a TIR of above 70% at any of the gestational ages measured, indicating that the previously suggested benchmark is difficult to actualize. Further, the results illustrated how spending less TIR, like within the durations measured in the current study, can still lead to positive patient outcomes.

“Our data indicate that good pregnancy outcomes can be achieved at lower TIR,” investigators wrote. “Rather than dichotomizing TIR to above or below a certain benchmark, practitioners can provide patients with nuanced information regarding predicted likelihood of outcome based on their current TIR.”

Study findings also demonstrated how small improvements might help alleviate the emotional and administrative burdens associated with the management of T1D, especially among pregnant patients.

“Prior qualitative work has consistently shown that gravidas with T1D experience guilt, panic, stress, frustration, and helplessness due to the unique demands of pregnancy and the clinical pressure from their care teams,” said investigators. “These negative feelings are likely to be exacerbated if healthcare providers set unachievable TIR targets and promote all-or-nothing thinking with the use of a dichotomous cutoff.”

READ MORE: Continous Glucose Monitoring Resource Center

1. Sobhani NC, Goemans 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 17, 2024. doi:10.1016/j.ajog.2024.01.010
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