Changes in heart rate from 5 s to 5 min after birth in vaginally delivered term newborns with delayed cord clamping

Objective To determine heart rate centiles during the first 5 min after birth in healthy term newborns delivered vaginally with delayed cord clamping. Design Single-centre prospective observational study. Setting Stavanger University Hospital, Norway, March-August 2019. Patients Term newborns delivered vaginally were eligible for inclusion. Newborns delivered by vacuum or forceps or who received any medical intervention were excluded. Interventions A novel dry electrode electrocardiography monitor (NeoBeat) was applied to the newborn's chest immediately after birth. The newborns were placed on their mother's chest or abdomen, dried and stimulated, and cord clamping was delayed for at least 1 min. Main outcome measures Heart rate was recorded at 1 s intervals, and the 3rd, 10th, 25th, 50th, 75th, 90th and 97th centiles were calculated from 5 s to 5 min after birth. Results 898 newborns with a mean (SD) birth weight 3594 (478) g and gestational age 40 (1) weeks were included. The heart rate increased rapidly from median (IQR) 122 (98-146) to 168 (146-185) beats per minute (bpm) during the first 30 s after birth, peaking at 175 (157-189) bpm at 61 s after birth, and thereafter slowly decreasing. The third centile reached 100 bpm at 34 s, suggesting that heart rates <100 bpm during the first minutes after birth are uncommon in healthy newborns after delayed cord clamping. Conclusion This report presents normal heart rate centiles from 5 s to 5 min after birth in healthy term newborns delivered vaginally with delayed cord clamping.

Automated summary

This study aimed to determine heart rate centiles in healthy term newborns delivered vaginally with delayed cord clamping during the first 5 minutes after birth. The results showed that heart rate increased rapidly within the first 30 seconds after birth, peaked at around 61 seconds, and slowly decreased thereafter. The study concluded that heart rates less than 100 bpm during the first minutes after birth are uncommon in healthy newborns after delayed cord clamping.