Acute responses to maternal smoking of the pulsatile movements in fetal aorta.

In order to further characterize the acute cardiovascular responses of the human fetus to maternal smoking, 17 women in late pregnancy were studied after smoking a single cigarette. The pulsations of the fetal descending aorta were recorded by means of an ultrasound scanner connected to a phase-locked echo-tracking instrument; the fetal ECG was recorded from abdominal electrodes. Both the level and the wave-form of the diameter pulse curve changed typically 3-25 min after the onset of smoking, concomitant with an increase in maternal and fetal heart rate. Apparent diastolic diameter and pulse amplitude increased, while the ascending part of the curve increased in slope and decreased in duration; the late decremental velocity was reduced. The propagation time from the onset of the fetal Q-wave to the arrival of the pulse wave at the site of recording was reduced. This study demonstrates for the first time the acute effects of maternal smoking on the pulsatile dynamics of fetal vessel walls, and the method suggests the possibility of estimating changes in the contractility of the fetal heart and the afterload in the fetal circulation.