Purpose of Investigation: The purpose is to identify factors related to postpartum hemorrhage (PPH) that are evaluated during regular prenatal check-ups. Materials and Methods: Obstetric and neonatal data were collected retrospectively for 1,922 women with singleton pregnancies who delivered vaginally. Results: Overweight women exhibited more severe PPH cases compared to normal PPH (p = 0.04). Of pre-pregnancy body mass index (BMI), gestational weight gain (GWG), gestational week of delivery, and neonatal body weight, neonatal body weight showed a significantly elevated risk for severe PPH (adjusted OR = 1.156, p < 0.001). Infant body weight was correlated positively with pre-pregnancy BMI, GWG, and gestational week of delivery (r = 0.194, r = 0.189 and r = 0.364, respectively). Pre-pregnancy BMI, GWG, and gestational week of delivery were associated with neonatal body weight (adjusted B = 0.169, 1.206 and 1.181, respectively; p < 0.001). Conclusion: Management of maternal body weight induces a safe delivery through controlling neonatal body weight. Content: Severe postpartum hemorrhage is associated with neonatal body weight which is influenced by maternal body mass index and weight gain.