Smoking Archives - Revista Brasileira de Ginecologia e Obstetrícia

Purpose: to evaluate the influence of cigarette smoking on uteroplacental, fetoplacental and fetal blood flow by obstetric Doppler velocimetry of the uterine, umbilical and middle cerebral arteries. Method: a prospective study with 42 healthy pregnant women, 20 of whom were smokers and 24 nonsmokers. Ultrasound was performed initially to determine the gestation time. The pregnant women next underwent pulsed and color Doppler velocimetry of the uterine, umbilical and middle cerebral arteries at the 24th, 28th, 32nd, 36th, and 40th week. The smokers were instructed not to smoke for at least two hours before the test. Results: the mean resistance index (RI) of the right and left uterine arteries was greatest in the smoking group at the 36th week [mean (SD) = 0.501 (0.034)], (p = 0.002). The pulsatility index (PI) of the umbilical artery was greatest in the smoking group at the 28th week [mean (SD) = 1.135 (0.182)], (p = 0.008). No difference in the PI of the middle cerebral artery (MCA) was detected between the two groups. However, the MCA/umbilical PI ratio was lower in the smoking group at the 32nd [mean (SD) = 1.977 (0.291)], (p = 0.027), and 36th week [mean (SD) = 1.850 (0.465)], (p = 0.014). Conclusion: it was concluded that smoking increases resistance in the uteroplacental and fetoplacental circulation while simultaneously reducing resistance in the MCA, imitating a "brain-sparing" effect, most likely due to chronic hypoxia.