Study of the Relationship between Body Mass Index and Birth Weight, Spontaneous Preterm Labor and Maternal Anemia in Shahid Akbarabadi Hospital, Tehran, 2008

Recent studies have reported that high and low maternal pre-pregnancy weight is accompanied with adverse pregnancy outcome including preterm labor and low birth weight or macrosomia. The purpose of the present study is to find the relationship between maternal pre-pregnancy body mass index (BMI) and spontaneous preterm labor and birth weight. This cohort study was performed on 576 pregnant women who referred to Shahid Akbarabadi hospital in Tehran in year 2008. 396 women finally finished the study. Maternal BMI was determined at the first prenatal visit (between 8-12 weeks of pregnancy) then the women were followed up to delivery. Gestational age at the time of delivery and neonatal weight were recorded and their results were investigated in four groups: underweight (BMI<20 kg/m2)، normal weight (BMI=20-24. 9 kg/m2)، over weight (BMI=25-29. 9 kg/m2) and obese (BMI=30-40 kg/m2). Data were analyzed using SPSS software (version 15)، T-test، ANOVA، Chi-square and Pearson correlation tests and linear regression model. P less than 0. 05 was considered statistically significant. The women in all BMI groups had no significant differences according to age، height، history of abortion and occupation. 21 women (5. 3%) were underweight، 198 women (50%) had normal weight، 117 women (29. 5%) were overweight and 60 (15. 2%) were obese. No case of morbidly obese was seen. Obesity had positive correlation with higher gestational age at the time of delivery (r=0. 213، p=0. 015) and more birth weight (r=0. 361، p=0. 008). In contrast، low birth weight had correlation with low maternal weight (r=0. 157، p=0. 041). Macrosomia was more in obese women (p=0. 022) and BMI had positive correlation with macrosomia (r=0. 224، p=0. 034). Preterm labor showed a negative correlation with BMI (r=-0. 124، p=0. 004) and preterm labor was seen more in women with lower BMI (p=0. 035). Overweight women was more high risk for macrosomia، while، low birth weight (LBW) and spontaneous preterm labor were seen more in underweight mothers.