Cord blood gas explainer
The short answer
A cord blood gas is blood taken from the umbilical cord right after birth. It shows how much acid built up in the baby's blood. That reflects the oxygen supply near the end of labor. 1
This explainer describes what each number measures. It does not interpret your baby's results, and it will not. Take the actual numbers to your neonatologist.
The numbers, up front
- What it measures
- Acid build-up in the baby's blood at birth, which reflects the oxygen supply near the end of labor 1
- The threshold guidance describes
- Professional guidance describes an umbilical artery pH below 7.0 with a base deficit of 12 mmol per litre or more as one of the findings associated with an acute event around the time of birth 1
- Two samples
- An arterial sample reflects the baby, a venous sample reflects the placenta. Both are usually taken 1
- A normal result is informative too
- A normal cord gas makes injury during labor much less likely, which is useful information in both directions 1
- It is one finding among several
- Guidance states that cause and timing are worked out from a pattern of findings taken together, not from a single test 1
This tool runs entirely in your browser. Nothing you type is sent anywhere, stored on any server, or seen by anyone including us. There is no analytics on this page. Nothing is saved when you close the page. You can check this yourself: turn off your internet connection and the tool still works.
Why this tool will not interpret your numbers
A cord blood gas is read alongside other things. The Apgar score scores. The newborn examination. The resuscitation record. The imaging. The placental pathology report. Guidance is explicit that cause and timing come from a pattern of findings taken together, not from one test. 1 2
A tool that turned two numbers into a conclusion would give you a false answer. Sometimes reassuring, sometimes frightening. Both would be wrong.
What this page can do is help you ask for the right things. The arterial and venous results. The time they were drawn. What your team makes of them in context.
Questions parents ask
What is a normal cord blood pH?
Ranges differ between laboratories, and between arterial and venous samples. That is why this site does not print a single normal value. Guidance does describe a threshold linked to an acute event. That is an umbilical artery pH below 7.0 with a base deficit of 12 mmol per litre or more. 1 Ask your team what your baby's values were, and what they mean in context.
Only one sample was taken. Does that matter?
It can. The arterial sample reflects the baby. The venous sample reflects the placenta. A single sample can also be mislabeled. Ask which sample each result came from. 1
No cord gas was taken at all. Is that a problem?
It means a useful piece of information is missing. Whether it should have been taken depends on the circumstances. It is a fair question to ask. 1
Words on this page, in plain English
- cord blood gas
- A blood sample taken from the umbilical cord right after birth. It shows how much acid built up in the baby's blood, which reflects oxygen supply near the end of labor.
- Apgar score
- A quick 0 to 10 score given at 1 and 5 minutes after birth. It rates color, heart rate, reflexes, muscle tone, and breathing. It describes the baby at that moment and it is not a prediction.
Where these facts come from
- American College of Obstetricians and Gynecologists and American Academy of Pediatrics. Neonatal Encephalopathy and Neurologic Outcome, Second Edition. 2014. www.acog.org/clinical/clinical-guidance/task-force-report/ar. Link checked September 3, 2026.
- American Academy of Pediatrics and American College of Obstetricians and Gynecologists. Committee Opinion 644, The Apgar Score. 2015. www.acog.org/clinical/clinical-guidance/committee-opinion. Link checked September 3, 2026.