Acute effects of maternal smoking on human fetal heart function.

M-mode echocardiography was used to evaluate fetal heart function following maternal smoking in 21 healthy smoking pregnant women between 24 and 39 weeks of uneventful gestation. Prior to smoking one cigarette (nicotine content 1.7 mg), a fetal M-mode echocardiographic examination was performed and repeated 5 and 10 min after maternal smoking. Maternal heart rate and systolic blood pressure increased 8.7% and 15.0%, respectively, immediately after smoking, while diastolic blood pressure remained unchanged. Fetal heart rate increased 4.3% and left ventricular diastolic and systolic diameters decreased 4.5% and 15.0%, respectively. No changes in right ventricular dimensions, ventricular ejection times, ventricular wall thickness or septal thickness were observed. Fractional shortening, mean velocity of fractional shortening, stroke volume and cardiac output of the left ventricle also remained unchanged subsequent to smoking. Thus, maternal smoking of one cigarette seems to elicit only a transitory acceleration in fetal heart rate without concomitant significant changes in fetal heart function.