Computerized analysis of acute and chronic changes in fetal heart rate variation and fetal activity in association with maternal smoking

OBJECTIVE: To investigate the acute and chronic changes In fetal heart rate and fetal activity in association with maternal smoking by means of a comp uterized 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 per iods, the smokers were allowed to smoke I cigarette, the nonsmokers were al lowed a short break of comparable time span. Fetal heart rate variation and fetal activity were recorded by a single 1.5-MHZ ultrasound transducer. Th e percentage of time spent in low and high fetal heart rate variation and f etal activity were analyzed by computer before and after the short break fo r nonsmokers and before and after the smokers smoked the 1 cigarette. Smoki ng-induced changes in Doppler umbilical artery recordings were also investi gated. Chronic exposure to cigarette smoke was objectively evaluated by mea suring the carbon monoxide concentration in expired air in all participatin g 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 activit y was decreased both in high and low fetal heart rate variation periods. Af ter maternal smoking, no acute changes were observed in fetal heart rate va riation, yet a reduction in fetal activity was noted; however, this only re ached statistical significance in periods of high fetal heart rate variatio n. No significant change in mean fetal heart rate was observed, yet a signi ficant reduction in the frequency of accelerations was noted. Smoking cause d an acute and transient increase In the mean pulsatility index in the umbi lical artery. CONCLUSION: The computer program was able to detect changes in fetal behavi oral variables in association with acute and chronic smoking. These changes may be suggestive of altered neurodevelopmental maturation possibly result ing from chronic fetal hypoxemia. This computer program offers a real possi bility that analysis of fetal behavioral variables can be brought into rout ine clinical practice. Incorporating an analysis of these behavioral variab les into smoking cessation programs may render them more successful.