Health of the mother is crucial for baby's growth. Body Mass Index (BMI) is a common measure to assess mother’s nourishment. Existing research suggests that undernourished mother can negatively impact the development of the placenta, which in turn affects blood flow and size. This can affect neonatal weight gain. However, there is a gap in the existing literature when it comes to linking the mother's BMI with the weight of the newborn. Hence the aim of the study is to assess the impact of early pregnancy BMI and gestational weight gain on neonatal birth weight. OBJECTIVES - Assess the association between Early pregnancy BMI and gestational weight gain on neonatal birth weight. MATERIAL and METHODS - An observational study was conducted at Dr D Y Patil Medical College & Hospital, Pimpri, Pune, involving 500 pregnant women with uncomplicated singleton pregnancies. All Ethical procedure was followed, and participants were recruited based on previous study data. Exclusions were made for systemic diseases. Pre-conceptional weight, height, weight gain during pregnancy, gestational age at delivery, and neonatal birth weight were recorded. Statistical analysis was performed. RESULTS– The study of 500 pregnant women found varied BMI distribution, with 55.7% normal, 18% underweight, and 18% overweight. Gestational weight gain and last trimester BMI changes were observed. Maternal BMI correlated with neonatal birth weight. Regional variations in neonatal birth weight were noted, prompting further research on low birth weight risks in underweight and obese females. Limitations include observer bias and a single-location study. CONCLUSION- Low BMI (underweight) and high BMI (obese) both contribute to low newborn birth weight. Gestational weight gain (GWG) is a crucial predictor of neonatal birth weight. Assessing GWGs is vital for implementing preventive measures against the risk of low birth weight.