Acute Effects of Maternal Smoking on the Uterine and Umbilical Artery Blood Velocity Waveforms

> Objective: The acute effects of smoking during pregnancy on the uterine and umbilical blood flow velocity waveform were assessed. Methods: Twenty-two chronic women smokers at a mean gestational age of 194.17 +/- 58.02 days and 21 women non-smokers at a mean gestational age of 193.24 +/- 34.71 days were studied. Systolic-diastolic (S/D) ratio, resistance index, and pulsatility index of uterine and umbilical arteries were measured in the control group and before and after smoking a single standard 100-mm filtered cigarette in the study group. Results: There was no significant change in the uterine artery and umbilical artery blood velocity waveform indices that could be attributed to the acute effect of smoking in the study group, but all of the uterine artery indices and S/D ratio in the umbilical artery were statistically higher in the study group in comparison with the control group both before and after smoking. Conclusion: Our results suggest that smoking causes an increase in vascular resistance of the placenta and umbilical cord when used chronically.