Postductal Pulse Oximetry (Oxygen Saturation Measurement)

What Does This Test Measure?

Postductal pulse oximetry measures arterial oxygen saturation (SaO₂), which reflects the percentage of oxygen carried by hemoglobin in your baby’s blood. The probe attaches to a finger or earlobe to continuously monitor oxygen levels, often as part of newborn screening for congenital heart defects or other respiratory conditions.

Why Is This Test Done?

This test is typically performed in newborns to evaluate oxygenation after the ductus arteriosus closes. It helps identify potential issues like heart defects, lung problems, or other conditions that may affect oxygen delivery. In some cases, it may be repeated if symptoms like poor feeding, breathing difficulties, or unusual color (pale/blue skin) are noticed.

When Might You Need This Test?

Your baby may undergo postductal pulse oximetry shortly after birth (within 1–48 hours) if they have risk factors for heart defects, such as a family history, premature birth, or signs of distress. It may also be done if your baby’s initial screening results were abnormal or if symptoms arise later.

What to Expect During the Test

The test is quick and painless. A small probe is placed on your baby’s finger or earlobe. The probe sends out harmless light to measure oxygen levels. You may feel a slight pinch as the probe is applied, but the procedure itself takes only a few minutes. No special preparation is needed.