Statistical analysis
Initially, we utilized univariate analysis to compare maternal
characteristics, glucose values during pregnancy, and T2DM outcome
stratified according to FPG levels during 1st trimester. FPG levels were
assessed in categorical increments of 10mg/dl (under 80, 80-90, 90-100,
100-110, and above 110 mg/dl). Maternal age and BMI were evaluated as
continuous and as categorical variables. Advanced maternal age was
evaluated with a cut-off of 35 and 40 years, and obesity was evaluated
as BMI ≥30 kg/m2. Other glucose levels, gestational
age at delivery, and time to follow-up were treated as continuous
variables, while hypertension, GDM, neonatal sex, and T2DM were treated
as categorical variables. Categorical variables were compared using χ 2
tests and the Mann-Whitney U test was used to test differences for
continuous variables. All the tests were 2-tailed, and
P < 0.05 was considered statistically significant.
Subsequently, we aimed to identify the optimal FPG threshold during
first trimester for predicting the risk of T2DM by employing receiver
operating characteristic (ROC) statistical analysis. The Youden index,
which maximizes the sum of sensitivity and specificity, determined the
best cutoff value. Furthermore, we compared the area under the curve
(AUC) for FPG, GDM, and the Youden index in predicting T2DM.
Lastly, given the variations in the follow-up duration for women in our
cohort, we calculated Kaplan-Meier hazard curves, which account for
these discrepancies. We also applied Cox proportional hazard models to
estimate the FPG level and GDM adjusted hazard ratios (aHRs) with 95%
confidence intervals (CI) for incident T2DM over the study period. The
selection of variables for the model was based on univariate association
with T2DM. Notably, we conducted a stratified analysis based on obesity
status (BMI ≥ 30 kg/m2), recognizing its potential impact on diabetes
risk and clinical approaches for prevention.