The short-term effect of smoking on fetal ECG

The number of women who smoke during pregnancy is significant even today. The harmful effects of smoking during pregnancy are well known but there are no data on the effects of smoking on fetal electrocardiography (ECG). The lack of data is in connection with the difficulties of recording fetal ECG through the maternal abdomen.

Third trimester pregnant women who were not able to give up the harmful passion of smoking despite repeated attempts of persuasion were recruited in the study on voluntary basis. The fetal ECG was recorded non-invasively through the maternal abdomen before, during and after smoking, then the data were processed offline. The electrophysiological measurements were performed by a self developed ECG device, which allowed the examination of the morphological differences in "true-to-form" fetal ECG in addition to studying the variability of fetal heart rate. The study involved nine pregnant women. The observed changes are presented through case studies of those pregnant women who showed the most significant anomalies.

Compared with the resting state fetal heart rate was increased during smoking. The short-term variability of fetal heart rate was narrowed, while the mother's heart rate did not change significantly - which was an indication of direct fetal stress. No explicit ischemic signs were detected in fetal ECG during smoking, however, in the increasing period of the fetal heart rate, the T wave morphology changed slightly, then it returned to normal.

Demonstrable by the electrophysiological methods, smoking has a direct effect on fetal cardiac function. The fetal heart rate variability shows a pattern during smoking which is a typical sign of stress conditions among adults. The results may have educational consequences as well. Understanding those, hopefully will help pregnant women give up this harmful addiction.