Background: To assess effect of body mass index on fetal outcome in pregnancy. Materials and Methods: One hundred ten first trimester women were selected. Parameters such as BMI, gestational age at delivery (in weeks), birth weight (in kg) APGAR Score, meconium- stained liquor, NICU admission etc. was recoded. Results: There were 30 underweight, 40 normal and 40 overweight patients. The difference was non- significant (P> 0.05). The mean APGAR score 1t 1 minute in underweight patients was 6.8, in normal was 6.2 and in overweight patients was 6.4. At 5 minutes was 8.9 in underweight, 8.7 in normal and 8.4 in overweight patients. The difference was non- significant (P> 0.05). 11% underweight and 34% overweight required NICU admission. The difference was significant (P< 0.05). 12% underweight and 38% overweight had meconium- stained liquor. The difference was significant (P< 0.05). 76% underweight, 91% normal and 100% overweight had >36 weeks gestational age. 40% underweight, 50% normal and 45% overweight had 2.5- 3 kgs birth weight. Apgar score at 1 min was seen in 90%, 92% and 88%, NICU admission in 11%, 0% and 34% and meconium- stained liquor in 12%, 14% and 38% underweight, normal and overweight babies respectively. The difference was significant (P< 0.05). Conclusion: Underweight and obese mothers had increased risk of adverse perinatal outcome.