Background: in the last decade, the prevalence of obesity has significantly increased in populations worldwide and becomes epidemic. Obesity has been documented by World Health Organization (WHO) as "a pandemic nutritional disorder. Egypt had the highest average Body Mass Index (BMI) and obesity in the world. Aim of the Work: evaluation of the possible effects of increased body mass index on pregnancy and measure its maternal, fetal and neonatal outcomes. Patients and Methods: the present study was approved from alazhar research ethical committee. The present study was carried out in Obstetrics and gynecology out-patient, Nasr city police hospital and El-hussien university hospital. Three hundred (300) pregnant women were included in the study; they were divided into3 groups: Group I 150 pregnant women with normal weight (BMI = 18.5 – 24.9 kg/m2). Group II: 75 pregnant women who are overweight (BMI = 25 – 29.9 kg/m2). Group III: 75 pregnant women who are obese (BMI >= 30 kg/m2). Groups were subjected to full history taking, clinical examination, obstetric palpation, ultrasound, investigations, antenatal care, post natal care and neonatal assessment. Results: statistical significant relationship between increased BMI and incidence of gestational hypertension, diabetes, postpartum hemorrhage and macrosomia. No Statistical significant relationship was found between increased BMI and incidence of cesarean rate, wound infection and intra uterine fetal retardation (IUGR). Conclusion: maternal obesity carries significant risks for the mother and fetus, including maternal outcomes as increased incidence of hypertension, gestational diabetes, cesarean rates, and postpartum hemorrhage. Fetal outcomes as macrosomia.