Cigarette smoking during pregnancy: acute effects on uterine flow velocity waveforms.

OBJECTIVE

To determine the acute effects of smoking during pregnancy on selected characteristics of the flow velocity waveform of the uterine artery.

METHODS

We studied 19 chronic smokers at a mean (+/- standard error) gestational age of 28 +/- 1 weeks. After informed consent was given, the uterine artery was located using ultrasound imaging with color flow mapping. The characteristic waveform was imaged by pulsed Doppler ultrasonography. Maternal heart rate and blood pressure and the systolic-diastolic ratio (S/D) and resistance index of the uterine artery were measured before (-10 and -1 minutes), during (+5 and +10 minutes), and after (+20 and +30 minutes) smoking two standard cigarettes in succession.

RESULTS

Maternal heart rate increased 27%, systolic blood pressure increased 8%, and diastolic blood pressure increased 19% with smoking (P < .001). The uterine artery S/D and resistance index decreased from 2.33 to 2.02 and from 0.55 to 0.49, respectively (P < .001).

CONCLUSION

The acute effects of smoking on maternal systemic hemodynamics probably influence the flow velocity waveform of the uterine artery and preclude any definitive interpretation of acute changes in downstream resistance.