https://www.resuscitationjournal.com/article/S0300-9572(26)00244-3/fulltext
A cohort study at Stavanger University Hospital, to investigate the relationship between umbilical arterial pH (UA-pH), heart rate and ventilation at birth. Among 3662 newborns the median (quartiles) UA-pH was 7.24 (7.19, 7.29). UA-pH <7.00 was identified in 20 (0.5%), 7.00–7.09 in 140 (3.8%), 7.10–7.19 in 833 (23%), and 7.20–7.50 in 2669 (73%) newborns. There was a weak and clinically insignificant linear correlation between UA-pH and first measured heart rate at 16 (11, 30) sec after birth (r=0.07, p<0.001), and no correlation with heart rate at one minute. Among newborns with UA-pH <7.00, only 50% were bradycardic with heart rate values <100 bpm in the first minute and one-third received ventilation at birth. Apgar scores were strongly associated with UA-pH.
Among ventilated newborns, first measured heart rate at 30 sec after birth showed a bimodal distribution (like Eilevstjønn et al has reported from Haydom, Tanzania) with peaks at 80–125 and 140–180 bpm, with lower median UA-pH values for newborns with heart rate <60 and >160 bpm.