The overall objective of this proposal is to quantify the bias in pulse oximeter reported oxygen saturation (SpO2) by evaluating its measures compared to the gold standard blood gas measured arterial oxygen saturation (SaO2) across race and skin pigmentation. The main question that the investigators intend to answer is whether

1. There is greater pulse oximeter bias and subclinical hypoxemia in (1a) Black compared to White infants, and (1b) dark versus light-pigmented infants
2. This bias increases with gestational and postnatal maturation
3. This bias is associated with adverse patient outcomes

The study investigators will conduct a prospective observational study involving 200 infants (0-3 months age) and compare simultaneously obtained pulse oximeter readings (SpO2) and co-oximeter measured blood gas arterial oxygen saturation (SaO2), among infants identified as Non-Hispanic Black and Non-Hispanic White. The investigators will also obtain an objective assessment of skin pigmentation using a non-invasive device, SkinColorCatch® (by Delfin Technologies Ltd, Finland) that provides (1) a melanin index and (2) an objective six-point categorization of skin color based on Individual Typology Angle (ITA). Therefore, the investigators will measure the pulse oximeter bias (SpO2-SaO2) across infants identified as Non-Hispanic Black and Non-Hispanic White, as well as among infants of various skin pigmentation. For infants that have an arterial line for more than one week, the researchers will measure pulse oximeter bias (SpO2-SaO2) on a weekly basis over time with skin maturation and pigmentation changes.

Inclusion Criteria:

• Signed Informed Consent
• Postnatal age less than 3 months corrected age
• Presence of an in-dwelling umbilical or peripheral arterial line
• Gestational age >= 25 weeks

Exclusion Criteria:

• Known skin pigmentary disorders
• Significantly impaired skin integrity
• Systemic bruising due to birth trauma
• Circulatory shock within last 48 hours
• Infants of peri-viable gestation (22-24 weeks)

All preterm (i.e. infant less than 37 weeks gestation) and term infants (i.e. infants >= 37 weeks gestation) that have an indwelling arterial line and are admitted to the ACH neonatal intensive care unit (NICU) and cardiovascular intensive care unit (CVICU).