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.