The Independent Contribution of Uterine Blood Flow to Birth Weight and Body Composition in Smoking Mothers.

ABSTRACT

OBJECTIVE: This study aims to evaluate the relationship of maternal smoking to uterine artery hemodynamics and examine independent contributions to birth weight and fetal body composition. STUDY DESIGN: Women were enrolled in a prospective randomized controlled study targeting smoking abstinence. Uterine artery Doppler ultrasound was performed and volumetric blood flow was calculated. Third trimester ultrasound estimates of fetal body composition were performed and birth weight was recorded. RESULTS: Uterine artery volumetric flow and resistance index (RI) were significantly correlated with birth weight adjusted for gestational age (R = 0.35, p = 0.002; R = - 0.27, p = 0.02). Volumetric flow was significantly associated with fetal fat mass (R = 0.30, p = 0.018). Smoking status did not have significant effects on lean body mass (t [61] = 0.60, p = 0.55), fat mass (t [61] = 1.67, p = 0.10), or volumetric flow (t = 0.86, df = 87, p = 0.39). Stepwise regression identified volumetric flow (ß = 0.81, 95% confidence interval [CI] 0.35-1.27, p < 0.001), maternal prepregnancy body mass index (ß = 16.04, 95% CI 2.57-29.50, p = 0.02), and fetal sex (ß = 346.28, 95% CI -532.64 to 159.91, p < 0.001, where male = 0 and female = 1) as independent contributors to birth weight adjusted for gestational age. CONCLUSION: No direct relationship of smoking to uterine artery hemodynamics was demonstrated. Volumetric flow was an independent contributor to birth weight and was associated with fetal fat deposition, while smoking was not independently associated with either outcome.