OBJECTIVE To analyze whether the obese women have an increased risk of pregnancy complications and adverse fetal outcome. METHODS The longitudinal prospective study was carried out in the Obst and Gynae department, IPGME and R, Kolkata. The study enrolled 422 pre-pregnant obese women with pregnancy as study population and equal number of non obese pregnant mothers as controls. Body mass index (BMI) was > or = 30.0 kg/m2 and 20-22 kg/m2 in obese and control group respectively. RESULTS In comparison to average weight pregnant women, obese pregnant women were at increased risk of gestational diabetes mellitus (19.43 vs 3.79%; p < 0.001), pregnancy induced hypertension (12.32 vs 2.36%; p < 0.001), pre-eclampsia (8.76 vs 3.31%; p < 0.001), preterm labor in less than 34 week gestation (7.58 vs 3.55%; p < 0.001), cesarean section (36.72 vs 17.53%; p < 0.001), instrumental deliveries (12.32 vs 5.21%; p < 0.001) and postpartum infection morbidities (9.95 vs 3.79%; p < 0.001). These women were more prone to develop overt diabetes (2.36% vs 0) and chronic hypertension (5.21 vs .47% ) in future as well. Neonates of obese women were mostly large for gestational age, macrosomic and they had high incidences of birth injuries, shoulder dystocia, premature deliveries, late fetal deaths and congenital malformations particularly spina bifida, cleft lip, cleft palate and heart defect. CONCLUSIONS As obesity is considered to be a modifiable risk factor, preconception counseling and creating awareness regarding health risks associated with over weight and obesity should be encouraged.