Abstract
BACKGROUND: While time in range (TIR) summarized over pregnancy is associated with adverse outcomes among individuals with preexisting type 1 or 2 diabetes, the impact of TIR trajectories with advancing gestation is unknown. OBJECTIVE: To identify glucose TIR trajectories across pregnancy and evaluate their association with perinatal outcomes among patients with preexisting diabetes. STUDY DESIGN: Retrospective, single-center cohort study of pregnant patients with type 1 or 2 diabetes who used continuous glucose monitoring (CGM) and delivered in 2019 to 2023. Weekly TIR (65-140 mg/dL) was computed starting at 10 weeks' gestation, and joint latent-class trajectory modeling identified discrete TIR trajectory groups. Patients were classified into groups, and multivariable logistic regression estimated the associations between groups and perinatal outcomes. RESULTS: Of 179 pregnant patients, 91 had type 1 and 88 had type 2 diabetes. We identified four TIR trajectory groups using data from over 5.1 million CGM measurements: (1) good control, stable (n=48), (2) moderate control, initial improvement, and late decline (n=22), (3) moderate control, late improvement (n=63), and (4) poor control, initial worsening and late improvement (n=46). All perinatal outcomes differed by TIR trajectory. Groups 2, 3, and 4 with suboptimal control in early pregnancy were associated with higher odds of preterm birth, indicated preterm birth, and NICU admission, compared to group 1. Groups 3 and 4, which had the lowest TIR during second and early third trimesters, were associated with higher odds of large-for-gestational-age (LGA). Only group 4 was associated with higher odds of preeclampsia and neonatal hypoglycemia. CONCLUSION: Achieving glycemic control in the second and early third trimesters during fetal and placental growth and development is important to reduce the risk of adverse pregnancy outcomes, particularly LGA. Third-trimester TIR decline may impact risk of preterm birth and NICU admission.