What Is the Purpose of Umbilical Cord Blood Gases?

Updated April 17, 2017

If you’re due to have a baby, your doctor may ask whether you want to have the umbilical cord blood gases sampled. There is some controversy in the medical community about whether the benefits of this procedure are worth the trouble and cost. It’s important you understand what you can gain from umbilical cord blood gas analysis so you can make an informed choice.


Umbilical blood cord gases are the pH, pCO2 and pO2 in the blood that runs through the artery and vein of the umbilical cord. Measuring these values determines the acidity level of the blood and can indicate how well-oxygenated the foetus was before delivery. The pH level is the main indicator used to measure fetal distress. An arterial pH below 7.05 is considered below normal.


To sample umbilical cord blood gases, a delivery nurse clamps off a section of the umbilical cord immediately after delivery. A technician draws blood from the isolated section in a syringe coated with heparin to keep the blood from clotting. It’s safe to wait up to an hour to do this--in most cases, if the baby shows no signs of distress, the clamped-off section of cord is discarded without drawing blood. If blood is drawn, a technician studies it in a blood gas analyzer to read the base acid levels.


Measures of umbilical cord blood gases can help physicians isolate the problem when a newborn has low Apgar scores or is otherwise in distress. If the pH level is below the normal range, this indicates the baby was poorly oxygenated before delivery, and the doctor knows how to help her recover. If the baby is in distress but has normal pH levels, the doctor knows he needs to look elsewhere to solve the problem.


It’s important to collect blood from both the umbilical artery and vein. In some cases, the venous blood may show pH levels within normal limits while the arterial blood is deficient. You need to be able to compare the two sides for an accurate reading and to get the full benefit of understanding what is causing fetal distress. Keeping the two sides together also helps delivery room personnel identify the correct sides.


Since the umbilical cord blood gases show the level of fetal oxygenation at the last moment before delivery, routine collection could be used to protect doctors from unfounded malpractice suits. If the foetus was in respiratory distress before delivery, the doctor can’t be blamed for a mistake during delivery that caused later problems.

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About the Author

Anne Madison has been a freelance writer since 2005. Her fiction has appeared in several magazines, including "Let's Worship" and "Drama Ministry." She has published numerous articles on eHow and other websites.