Neonatal heart rate variability in relation to smoking during pregnancy

Objective To evaluate the effects of prenatal nicotine exposure on the neur ogenic control of neonatal heart rate. Methods Thirty-six healthy newborns (20 boys and 16 girls) with a mean age of 52 h were examined by means of Hotter ECG recordings during quiet sleep (QS), active sleep (AS) and awake states. Seventeen of the mothers had smok ed during pregnancy and 19 were non-smokers, To compare the neonatal autonomic control of heart rate between the smoking and the non-smoking groups, heart rate variability (HRV) was calculated wi th spectral analysis of R-R intervals and the mean values of 2-min epochs. Total power, low-frequency power (LF), high-frequency power (HF) and the lo w to high frequency ratio (LF/HF) were examined. The LF/HF ratio is conside red to reflect sympathovagal balance. Results Prenatal exposure to nicotine did not influence the total power or the high- or low-frequency components. Boys had a tendency to higher HRV th an girls and this was significantly higher at LF during 95. On combining th e effects of maternal smoking and gender, boys with smoking mothers had a l ower LF/HF ratio than boys with non-smoking mothers: 0.87 +/- 0.37 and 1.34 +/- 0.51, respectively (p < 0.05). Conclusion Smoking during pregnancy may have a different effect on the symp athovagal balance in the development of the fetal male autonomic nervous sy stem than on that of the female.