Background/Aims: It is known that high pre-preg-nancybody mass index (BMI) and high gestational weight gain both can cause many adverse pregnancy outcomes. High pre-delivery BMI (PD-BMI), though theoretically could do similar effects, is rarely been studied. The objectives of this study were to show the distribution of PD-BMI of the delivery women and to identify its correlation with adverse pregnancy outcomes. Methods: This study was a cross sectional study. Data were collected retrospectively from hospital electronic database of Lampang Regional Hospital (LPH) along with manual retrieval from medical charts and labor records. Data of all pregnant women who delivered at labor room were collected from 1st February 2011 to 31st August 2012. After preterm and multifetal pregnancies were excluded, 4999 cases were into the analysis. Descriptive and inferential data analyses were used with both univariate and multivariate methods. Results: In this group of women, 93.9% were in the PD-BMI range of 20.0 -34.9 kg/m². After multivariate analysis was used, higher PD-BMI was shown to be correlated with higher cesarean section, neonates weighing ≥3500 gmand long neonatal length with relative risk (RR) and 95% confidence interval (95% CI) of 1.11 (1.09 - 1.13), 1.15 (1.12 - 1.17) and 1.07 (1.05 - 1.09), respectively. Conclusions: High PD-BMI was correlated with multiple adverse pregnancy outcomes. Interestingly, their effect sizes were much smaller comparing to high pre-pregnancy BMI and high gestational weight gain. It confirmed the current recommendations to monitor pre-pregnancy BMI and gestational weight gain to avoid unwanted morbidities.