Impact of passive smoking on uterine, umbilical, and fetal middle cerebral artery blood flows.

Purpose: The aim of this study was to evaluate the influence of passive maternal smoking on blood flow velocities in arteries of the fetal-placental-maternal circulation.

Materials And Methods: A total of 79 pregnant women in their third trimester, including 33 passive smokers, 23 active smokers, and 23 nonsmoking controls, were enrolled in the study. Fetal biophysical indices were evaluated with B-mode scanning, whereas blood flow waveforms of uterine, umbilical, and fetal middle cerebral (MCA) arteries were analyzed with Doppler ultrasonography.

Results: There were significant differences among active smokers vs. passive smokers vs. controls with regard to the presence of a uterine artery diastolic notch (39.1% vs. 18.2% vs. 4.3%; P = 0.012); ratio of peak systolic/end-diastolic velocity of fetal MCA [3.73 ± 1.27 vs. 4.26 ± 1.20 vs. 5.00 ± 2.15, analysis of variance (ANOVA) P = 0.026]; resistance index of fetal MCA (0.74 ± 0.08 vs. 0.75 ± 0.07 vs. 0.80 ± 0.09; ANOVA P = 0.014); ratio of fetal MCA/umbilical artery resistance index (1.27 ± 0.20 vs. 1.24 ± 0.14 vs. 1.39 ± 0.21; ANOVA P = 0.011); and ratio of fetal MCA/umbilical artery pulsatility index (1.56 ± 0.44 vs. 1.63 ± 0.43 vs. 1.97 ± 0.54; ANOVA P = 0.046).

Conclusion: Effects of passive maternal smoking on the fetal-placental-maternal unit were comparable to those with active maternal smoking as determined by the means of increased resistance in the maternal vasculature and adaptive changes of cerebroplacental circulation for maintaining fetal cerebral circulation.