The effect of prepregnancy body mass index on birth weight, preterm birth, cesarean section, and preeclampsia in pregnant women

Objective: The objective of this study is to determine the impact of maternal prepregnancy BMI on birth weight, preterm birth, cesarean section, and preeclampsia among pregnant women delivering singleton life birth. Methods: A cross-sectional study of 4397 women who gave singleton birth in Tehran, Iran from 6 to 21 July 2015, was conducted. Women were categorized into four groups: underweight (BMI < 18.5 kg/m²), normal (BMI 18.5-25 kg/m²), overweight (BMI 25-30 kg/m²) and obese (BMI >30 kg/m²), and their obstetric and infant outcomes were analyzed using both univariate and multivariate logistic regression. Results: Prepregnancy BMI of women classified 198 women as underweight (4.5%), 2293 normal (52.1%), 1434 overweight (32.6%), and 472 as obese (10.7%). In comparison with women of normal weight, women who were overweight or obese were at increased risk of preeclampsia (odds ratio (OR) = 1.47, 95% CI = 1.06-2.02; OR = 3.67, 95% CI = 2.57-5.24, respectively) and cesarean section (OR = 1.21, 95% CI = 1.04-1.41; OR = 1.35, 95% CI = 1.06-1.72, respectively). Infants of obese women were more likely to be macrosomic (OR = 2.43, 95% CI = 1.55-3.82). Conclusion: Prepregnancy obesity is a risk factor for macrosomia, preeclampsia, and cesarean section and need for resuscitation.