Association of Pre-Gestational Obesity with Clinical Presentation and Perinatal Outcomes in Women with Gestational Diabetes Mellitus

Background/Objectives: PGO is a risk factor for GDM and adverse perinatal outcomes, but its association with clinical presentation and outcomes among affected women remains incompletely characterized. This study compared clinical, metabolic, maternal, and neonatal outcomes in women with GDM according to PGO status. Methods: This was a retrospective observational study of 300 women diagnosed with GDM between January 2022 and December 2023 at a tertiary hospital. Women were classified by pre-pregnancy BMI as with or without PGO (≥30 kg/m2). Clinical, biochemical, obstetric, and neonatal data were analysed. Multivariable logistic regression assessed factors independently associated with recorded GMD diagnosis before 24 weeks, insulin requirement, and macrosomia. Results: PGO was present in 41% of women. PGO was associated with recorded GDM diagnosis before 24 weeks (aOR 2.71; 95% CI 1.64–4.50; p < 0.001) and insulin requirement (aOR 3.08; 95% CI 1.77–5.39; p < 0.001). HbA1c remained slightly higher in women with PGO. Macrosomia was more frequent with PGO (12.2% vs. 4.5%; p = 0.025) and remained independently associated after adjustment (aOR 3.54; 95% CI 1.41–8.91; p = 0.007). In women with PGO, excessive gestational weight gain was associated with higher odds of macrosomia after adjustment for gestational age at delivery and pre-gestational BMI (aOR 10.89; 95% CI 2.91–40.76; p < 0.001). Conclusions: PGO was associated with a diagnosis of GDM before 24 weeks, increased insulin requirement and higher odds of macrosomia. These findings highlight the importance of preconception metabolic optimization, weight monitoring during pregnancy, and future risk stratification in clinical practice.