Oxygen saturation immediately after birth

Pulse oximetry provides the means for continuous non-invasive monitoring of oxygen saturation (SpO₂). Although not currently used for the purpose, recent international guidelines suggest that pulse oximetry may be useful in the assessment of newborns who require urgent resuscitative measures at the time of birth. 

Specifically it is envisaged that measured SpO₂ would guide the use of supplemental oxygen in these sick babies. Unfortunately there is a paucity of information regarding normal SpO₂ values during the crucial minutes following birth. Clearly this information gap must be filled before pulse oximetry can be effectively exploited in the delivery room, and two recently published studies, one from Australia, the other from Canada, go a long way in this regard.

The principal aim of both studies was to demonstrate the feasibility of routinely measuring SpO₂ at the time of birth, and to document the changes in SpO₂ during the first 10 minutes of life among healthy, full-term or near-full-term babies. The two studies were of very similar design and both utilized the same state-of-the-art motion-resistant pulse oximeter for monitoring SpO₂. 

A total of 175 babies were monitored in the Australian study and 115 babies were monitored in the Canadian study. At the moment of cord clamping, the pulse oximeter sensor was applied to each baby’s right wrist or hand. 

In both studies the median time to establish a reliable signal was 80 seconds. In the Australian study the median SpO₂ at 1 minute of life was 63 % (range 53-68 %). A gradual rise with time followed, so that at 5 minutes of life median SpO₂ was 90 % (range 79-91 %). A similar rise, albeit slightly slower, was observed in the Canadian study population. 

Here the median SpO₂ at 5 minutes was 87 % (range 80-90 %), and it was 8 minutes before median SpO₂ reached the normal postnatal value of 90 %. Compared with those babies delivered vaginally, those delivered by cesarian section had slightly lower SpO₂ at 5 minutes of age, and took slightly longer to achieve SpO₂ of 90 %.

The two studies have independently documented the rapid rise in oxygen saturation from 60-90 % that normally occurs during the first 5-10 minutes of life. The feasibility of routine pulse oximetry monitoring during this period has been demonstrated.