Maternal obesity and malnutrition both impact the fetomaternal outcomes. This prospective observational study conducted at a tertiary care center in Jharkhand, India, aimed to assess fetomaternal outcomes across different BMI categories. A total of 160 primigravida women with singleton pregnancies were categorized based on WHO BMI classifications (underweight, normal weight, overweight, and obesity). Maternal and fetal data were collected, including demographic details, medical histories, mode of delivery, and neonatal outcomes. Statistical analysis of the data revealed significant associations between higher BMI categories and increased incidence of hypertensive disorders, gestational diabetes, cesarean deliveries, and neonatal complications. Also mothers with low BMI or poor nutritional status were prone to have preterm and low birthweight babies. These findings underscore the importance of BMI monitoring and management in improving maternal and fetal health outcomes. Method: This prospective observational study was done in Department Obstetrics and Gynaecology, Rajendra Institute of Medical Sciences,Ranchi. Written and informed consent was obtained by the women satisfying the inclusion and the exclusion criteria. Detailed history was taken and body mass index was calculated by weight in kg/height in meter square.the women were followed up during antepartum, intrapartum and postpartum period for variables neonatal outcomes were also documented. Result: Significant associations were observed between maternal BMI categories and various pregnancy-related conditions and outcomes. Higher BMI categories (overweight and obesity) correlated significantly with increased incidence of hypertensive disorders (p = 0.017), gestational diabetes (p < 0.001), and cesarean deliveries (p < 0.001). Additionally, higher BMI was associated with prolonged labor duration (p = 0.004) and increased incidence of severe perineal tears (p = 0.004). Neonatal outcomes such as macrosomia , NICU admissions, also show correlation with BMI. Conclusion: Maternal BMI serves as a crucial determinant of pregnancy outcomes, influencing the incidence of gestational complications and neonatal health. This study underscores the importance of BMI monitoring in prenatal care settings to improve maternal and fetal health outcomes. Future research should explore longitudinal effects and interventions targeting maternal obesity to enhance maternal healthcare strategies.