Glucose time in range trajectories during pregnancy and association with adverse perinatal outcomes: a joint...

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.

To identify glucose TIR trajectories across pregnancy and evaluate their association with perinatal outcomes among patients with preexisting diabetes.

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.

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.

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.