Preterm Infants Who Did Not Need Positive Pressure Ventilation Had a Lower Heart Rate Immediately After Birth Than Healthy Term Infants.

Aim: Our aim was to use electrocardiograms immediately after birth to determine the heart rates of healthy newborn infants by gestational age and mode of delivery.

Methods: This prospective observational study was performed in two Norwegian hospitals from March 2019 to June 2021. We included infants with gestational ages of ≥ 28 weeks and no need for positive pressure ventilation. Continuous heart rate data were collected using dry electrode technology and were used to create percentile charts and compare heart rates by groups.

Results: We enrolled 214 preterm and 2191 term newborn infants. The median (quartiles) heart rate at 60 s of age was 166 (150-181) beats per minute for preterm infants and 174 (158-187) for term infants (p < 0.05). Term infants born using vacuum extraction, forceps or emergency Caesarean sections had significantly higher heart rates than term infants born by unassisted vaginal deliveries or planned Caesarean sections. The median heart rates of the groups were all within the normal range.

Conclusion: This study provided normative heart rate data for healthy newborn infants, by gestational age and delivery mode. Although the differences between the groups were statistically significant, they were of limited clinical significance and would not support changes in neonatal resuscitation measures.