Effects of maternal cigarette smoking on fetal trunk movements, fetal breathing movements and the fetal heart rate.

The acute effect of maternal cigarette smoking was studied in 10 patients between 37 and 40 weeks gestation. There was a significant reduction in the percentage of time the fetus spent moving during the first 16 min of smoking (P less than 0.02). No significant changes were seen in the proportion of time the fetus spent breathing or the number of times the fetus changed from high or intermediate to low heart period variability. There were significant reductions in the number of accelerations (P less than 0.01), beat-to-beat variation (P less than 0.01) and root-mean-square of the deviation around the mean (P less than 0.02).