The effects of body mass index, smoking and anemia on fetal birth weight

Objective Fetal growth is an important indicator of fetal health. Low birth weight (LBW) is also associated with increased perinatal morbidity and mortality. Numerous factors that affect fetal weight have been identified. In this study, we aimed to investigate the effect of body mass index, smoking, and anemia on fetal birth weight on term pregnant women who had vaginal delivery in our clinic. Methods This study is a retrospective cross-sectional study. This study included patients who had a spontaneous vaginal delivery at our hospital between January 1st, 2018, and June 15th, 2020. Measurements of hemoglobin (Hb) and hematocrit (Hct) levels during birth supported the diagnosis of anemia. Hb levels were compared in three categories in this study: (1) Hb<10 g/dL; (2) ≥10<11 g/dL; and (3) Hb ≥11 g/dL. Anemia was defined as having a Hb level <11 mg/dL. Birth weight was categorized as LBW <2500 g; normal birth weight (NBW) as ≥2500–3999 g, and macrosomia as ≥4000 g. Results Analysis was performed on 1428 pregnant women. There was a statistically significant difference for the Hct and Hb subgroups between the groups (p<0.05). Fetal birth weight was found higher in the non-smoking group than in the smoking group (3302.1± 381.5 g vs. 2839.7±491.5 g; p<0.001). Body mass index (BMI) and Hb levels positively predicted fetal birth weight (β=0.134; p<0.001 and β=0.051; p=0.046), smoking was negatively predicted fetal birth weight (β=-0.245; p<0.001). Conclusion BMI, Hb levels, and smoking status during mothers’ delivery are effective on fetal weight. Smoking was the strongest predictor of fetal birth weight compared with the other variables.