Vacuum extraction and autonomic balance in human infants

The impact of delivery mode on the cardiac autonomic balance was studied in a sample of 101 full term appropriate for gestational age (AGA) human infants. Cardiac autonomic balance was measured by assessing basic heart rate, and two indicators of vagal tone, the Root Mean Square of Successive Differences (RMSSD) and Standard Deviation of NN-intervals (SDNN) as two different measures of short-term heart rate variability at 2, 6, and 16 weeks postnatal age. Sixty-seven infants were delivered spontaneously, 29 by cesarean section and five by vacuum extraction. Children delivered by vacuum extraction had a significantly lower basic heart rate (P=0.01), higher RMSSD (P=0.0003) and higher SDNN (P=0.0001) at two, but not at six and sixteen weeks, indicating a temporary elevation of cardiac vagal tone in these infants. These data indicate a potential transitory impact of vacuum extraction on autonomic balance persisting until at least two weeks postnatal age.