Association between extrapolated time in range and large for gestational age infants in pregnant women with type 1 diabetes

To evaluate the association between extrapolated time in range (eTIR), measured by self-monitoring of blood glucose (SMBG), and large-for-gestational-age (LGA) infants in pregnancies with type 1 diabetes (T1D). Retrospective cohort analysis including singleton pregnancies with T1D who started antenatal care before 20 gestational weeks and delivered live newborns at a Brazilian hospital between 2010 and 2019, with LGA fetuses as the main outcome. Glycemic records acquired using SMBG were categorized as eTIR, extrapolated time below range (eTBR), and extrapolated time above range (eTAR). Women were divided into two groups (LGA and adequate for gestational age [AGA]) and compared regarding clinical characteristics, obstetric outcomes, and frequencies of eTIR, eTBR, and eTAR. Logistic regression analysis verified the independent predictive variables for LGA infants. Data from 125 pregnancies were analyzed. For the first, second and third trimesters, each 1 % increase in eTIR was associated with a decreased risk of LGA by 2.9 % (OR: 0.971; 95%CI: 0.945–0.998), 2.5 % (OR: 0.975; 95%CI: 0.951–0.999) and 2.3 % (OR: 0.977; 95%CI: 0.955–0.998) and each 1 % increase in eTAR was associated with an increased risk of LGA by 2.7 % (OR: 1.027; 95%CI: 1.005–1.050), 3.9 % (OR: 1.039; 95%CI: 1.014–1.063) and 4.6 % (OR: 1.046; 95%CI: 1.018–1.075), respectively. The concept of TIR can be extrapolated to patients undergoing SMBG to assess the risk of LGA infants in pregnant women with T1D. •Novel targets based on CGMS, such as TIR, are being standardized as predictors of obstetric outcomes.•Nonetheless, SMBG remains the main method for evaluating glucose levels in people with T1D.•TIR is an independent predictor of LGA infant outcome in all gestational trimesters.•TIR can be extrapolated to SMBG to assess the risk of LGA infants in pregnant women with T1D.