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A Deeper Look Into Arterial Cord Blood Gas Values

By Rheingold Giuffra Ruffo Plotkin & Hellman LLP

What is an umbilical cord blood gas level?

Once a baby has been delivered, the medical team draws blood directly from the infant’s umbilical cord artery. This blood is further examined to see if there were any complications before or during the delivery that resulted in a lack of oxygen.

Oxygen deprivation, otherwise known as birth asphyxia can cause:

  • Brain damage
  • hypoxic-ischemic encephalopathy
  • Periventricular leukomalacia
  • Intraventricular hemorrhages
  • Cerebral palsy
  • Seizure disorders
  • Intellectual disabilities
  • Developmental delays

Healthy arterial cord blood gas levels for a term newborn are as follows:

  • pH: 7.18 – 7.38
  • PCO2: 32 – 66 (mmHg)
  • HCO3-: 17 – 27 (mmol/L)
  • PO2: 6 – 31 (mmHg)
  • Base excess (BE): -8 – 0 (mmol/L); (Base deficit (BD): 0 – 8)

Healthy arterial cord blood gas levels for a preterm newborn are as follows:

  • pH: 7.14 – 7.4
  • PCO2: 32 – 69 (mmHg)
  • HCO3-: 16 – 27 (mEq/L)
  • BE: -7.6 – 1.3 (mmol/L); (BD: 1.3 – 7.6)

Understanding these numbers:

The most important values to examine are the pH and BE/BD levels. A pH below 7.18 and a BE lower than -8 are indications that the baby suffered from oxygen deprivation.


The pH level describes the acidity of the infant’s blood. If the pH value is low, the infant’s blood is acidic, which occurs as a result of either an elevated PCO2 and/or an increased number of acidic by-products caused by anaerobic metabolism. Typically, an elevated PCO2 value means that the fetus is producing more CO2 than can be properly eliminated through circulation.

High PCO2 levels are most commonly seen in cases of umbilical cord compression, which prevents blood from moving to and from the baby properly. When a baby/s cells are deprived of enough oxygen, the cells switch from aerobic metabolism to anaerobic metabolism.

A low arterial cord pH value can also help determine if hypoxia around the time of delivery was severe enough to cause hypoxic-ischemic encephalopathy (HIE). If the pH value is low, the medical team is alerted that the newborn may be suffering from HIE or various other forms of brain damage.

Research highlights a strong association between a pH value less than 7.0-7.24 and significant health issues such as HIE, intraventricular hemorrhaging, PVL, and cerebral palsy occurring in the newborn.


BE/BD stands for base excess and base deficit. A base deficit is defined as the amount of strong base that is needed to return the pH to a normal value. The more negative the BE value is, the greater the concentration of metabolic components that contributed to the acidic pH value. Research has proven that a BE value equal to or lower than -12 is a strong predictor that the newborn infant will face various complications.

Labor and Delivery Problems

Unfortunately, a normal BE/BD and pH level do not rule out the fact that the newborn experienced oxygen deprivation before or during delivery. For instance, a baby may have suffered an oxygen-depriving event such as a complete placental abruption right before birth. In cases like this, the cardiopulmonary system does not have enough time to reflect the oxygen deprivation, resulting in normal arterial cord gas values.

Birth Injuries

Other examples of complications occurring during or near the time of birth that can cause oxygen deprivation include:

  • A delayed emergency C-section
  • Umbilical cord problems, such as a nuchal cord, umbilical cord prolapse, short cord, and a true knot in the cord
  • Oligohydramnios
  • Premature rupture of the membranes (PROM)/premature birth
  • Ruptured uterus
  • Placental abruption
  • Prolonged and arrested labor
  • Placenta previa
  • Preeclampsia/eclampsia
  • Postmaturity syndrome
  • Fetal stroke
  • Intracranial hemorrhages
  • Anesthesia mistakes

If your baby experienced any birth injuries, please contact our attorneys at Rheingold, Giuffra, Ruffo, and Plotkin. Our firm has handled numerous birth injury cases and has a long-standing track record of successful results for our clients. Our staff includes registered nurses who are well-versed in medical issues resulting from birth trauma and delivery complications. In addition, we have access to expert witnesses who help us build compelling cases for our clients.

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