Objective: To investigate the acute and chronic changes in fetal heart rate and fetal activity in association with maternal smoking by means of a computerized fetal behavior assessment program.
Study design: In 13 term nonsmokers and 13 term smokers, fetal behavior was analyzed for 2 consecutive periods of >60 minutes. In between these 2 periods, the smokers were allowed to smoke 1 cigarette, the nonsmokers were allowed a short break of comparable time span. Fetal heart rate variation and fetal activity were recorded by a single 1.5-MHZ ultrasound transducer. The percentage of time spent in low and high fetal heart rate variation and fetal activity were analyzed by computer before and after the short break for nonsmokers and before and after the smokers smoked the 1 cigarette. Smoking-induced changes in Doppler umbilical artery recordings were also investigated. Chronic exposure to cigarette smoke was objectively evaluated by measuring the carbon monoxide concentration in expired air in all participating women after breath holding.
Results: Fetuses chronically exposed to cigarette smoke spent significantly more time in a low fetal heart rate variation pattern, while fetal activity was decreased both in high and low fetal heart rate variation periods. After maternal smoking, no acute changes were observed in fetal heart rate variation, yet a reduction in fetal activity was noted; however, this only reached statistical significance in periods of high fetal heart rate variation. No significant change in mean fetal heart rate was observed, yet a significant reduction in the frequency of accelerations was noted. Smoking caused an acute and transient increase in the mean pulsatility index in the umbilical artery.
Conclusion: The computer program was able to detect changes in fetal behavioral variables in association with acute and chronic smoking. These changes may be suggestive of altered neurodevelopmental maturation possibly resulting from chronic fetal hypoxemia. This computer program offers a real possibility that analysis of fetal behavioral variables can be brought into routine clinical practice. Incorporating an analysis of these behavioral variables into smoking cessation programs may render them more successful.