Objective: Our purpose was to compare Doppler-derived cardiac time intervals and cord plasma levels of catecholamines in vaginally and cesarean delivered neonates.
Methods: Doppler echocardiographic assessments of fetal and neonatal cardiac time intervals were made to determine differences in circulatory changes in 8 neonates delivered vaginally and 12 delivered by elective cesarean section. Aortic and pulmonary acceleration time (AT), ejection time (ET), and the AT/ET ratio in systole were assessed at various time points from antenatal to 72 h after delivery. Umbilical artery blood gas and acid-base values, and cord blood concentrations of epinephrine and norepinephrine were also measured.
Results: Umbilical artery blood pH in the cesarean section group was significantly lower than that in the vaginal delivery group (p < 0.05). Base deficit in umbilical artery blood and cord blood norepinephrine in cesarean delivered neonates were significantly higher than those in vaginally delivered neonates, respectively (p < 0.05). There were no significant changes in aortic cardiac time intervals between the 2 groups at any of the various time points. However, pulmonary AT and the AT/ET ratio were significantly lower in the normal vaginal delivery group than those in the cesarean section group 6 h after delivery (p < 0.05).
Conclusions: The lower AT and AT/ET ratio of the pulmonary artery in vaginally delivered neonates may reflect an increase in pulmonary vascular resistance, indicating transient pulmonary hypertension. The findings were the reverse of what might be expected from an elevated pulmonary vascular resistance and transient pulmonary hypertension in cesarean delivered neonates.