en عمومى General پژوهشي Research Abstract Background: In order to clarify the association between maternal body mass index and gestational weight gain with maternal and fetal complications. Methods: In this descriptive cross-sectional investigation, pregnant women with 18-30 years of age referring to health care centers in sari, Mazandaran, Iran were enrolled Results: In this study 400 pregnant women were examined. The mean ± SD age of study population was 27.8 ± 4.8 years. 125 participants (31.3%) were presented with low IOM and 77 patients (19.3 %) were high IOM. The mean weight of fetal birth weight was 3.2±0.4 kg. Weights of 377 newborns were between 2500 to 4000 gr. 8 cases (2%) had low birth weight and 15 cases (3.8%) were over than 4000 gr. The mean ± SD of newborns length was 49.6 ±5.6 cm. The mean ± SD of head circumflex of newborns was 34.4± 3.6 cm. There was no significant association between mothers BMI and infant head circumflex, height and weight. There was no significant correlation between macrosomia and mothers IOM (p=0.07). There was no significant association between infants’ weight and mothers IOM (p=0.3). There was significant correlation between BMI and IOM (p=0.000). Preterm delivery was noted in 6 women (6.5%) with BMI more than 29 and in 1 participant (1.2%) with BMI of 26.1 to 29. There was significant association between BMI and preterm birth (p=0.001). Gestational diabetes mellitus was noted in 6 women with BMI more than 29 (p=0.000). Gestational diabetes mellitus was reported in 6 women with normal IOM (p=0.04). Preeclampsia was noted in 3 women with BMI of 26.1 to 29 (p=0.04). Conclusion: Pregravid overweight or gaining weight will increase the risk of overweight birth. body mass index, weight, birth weight 318 323 http://intjmi.com/browse.php?a_code=A-10-1-109&slc_lang=en&sid=1 Mohammad Khademloo 10031947532846002513 10031947532846002513 No Department of Community Medicine, Mazandaran University of Medical Sciences, Sari, Iran Hasan Karami 10031947532846002514 10031947532846002514 Yes Department of Paediatrics, Mazandaran University of Medical Sciences, Sari, IR Iran Mandana Yasari 10031947532846002515 10031947532846002515 No Department of Community Medicine, Mazandaran University of Medical Sciences, Sari, Iran