Michigan birth injury attorneys answer an FAQ: What are normal umbilical cord blood gas results?

Michigan birth injury attorneys answer an FAQ: What are normal umbilical cord blood gas values?

As soon as a baby is born, the medical team usually draws blood from the baby’s umbilical cord artery.  This blood is analyzed to determine if the baby experienced a complication shortly before or during delivery that deprived her of oxygen.  Oxygen deprivation, called birth asphyxia, can cause brain damage, hypoxic ischemic encephalopathy (HIE), periventricular leukomalacia (PVL – usually seen in premature babies), intraventricular hemorrhages (brain bleeds) and lifelong conditions, such as cerebral palsy (CP), seizure disorders, intellectual disabilities and developmental delays.  Normal umbilical cord blood gas values are listed below.


Normal arterial cord blood gases for a term newborn:

  •     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)

Normal arterial cord values in a preterm newborn:

  •     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)

*The “P” in PCO2 and PO2 stands for “partial pressure,” which is how these gases are measured.


We have written extensively about umbilical cord blood gas interpretation.  The key point for parents to know is that the pH and BE / BD are the main values examined by the medical team.  The other values impact the pH and BE, but pH and BE are the main numbers examined to determine if the baby suffered from a lack of oxygen to her brain either shortly before or during delivery.  Terms associated with oxygen deprivation are asphyxia, hypoxia (decreased oxygen at the tissue level) and ischemia (restricted or reduced blood flow).

A pH below 7.18 and base excess that is more negative than -8 are indications that the newborn suffered oxygen deprivation.  Of course, oxygen deprivation may still have taken place, even if these values are normal.


A low arterial cord pH is probably the single most important value used to determine if hypoxia near the time of delivery was severe enough to cause hypoxic ischemic encephalopathy (HIE).  If the pH is low, the medical team should be alert to the fact that the baby may have HIE or other forms of brain damage.  A pH below 7.18 for a term infant is considered abnormally low, but research shows a strong association between a pH of less than 7.0 – 7.24 and adverse outcomes in the baby, such as HIE, intraventricular hemorrhages (IVH, brain bleeds), periventricular leukomalacia (PVL) and cerebral palsy.

PH is the acidity of the baby’s blood.  If the pH is low, the blood is acidic, which means that at birth, the baby had an elevated PCO2 and / or an increased number of acidic by-products caused by anaerobic metabolism, mainly lactic acid.

In general an elevated PCO2 means that the fetus is producing more PCO2 than can be eliminated through circulation.  In other words, PCO2 is not readily diffusing from the umbilical artery and capillaries into the maternal placenta and maternal circulation.  An accumulation of PCO2 is most commonly seen in umbilical cord compression, which hinders or prevents the movement of blood to and from the baby.  In cord compression, PO2 will typically be low, and if the compression persists, there will be progression to metabolic acidosis with accumulation of lactic acid.

When a baby’s cells are deprived of sufficient oxygen, the cells will switch from aerobic metabolism to anaerobic metabolism.  This is another reason a compressed umbilical cord can cause a low pH / acidic blood; the cells don’t have sufficient oxygen to do work in the normal way and meet energy demands (aerobic metabolism), so the anaerobic system is used, which is a system that does not require oxygen.  The anaerobic system is only supposed to be used for very short periods of time.  Lactic acid is one of the end products of anaerobic metabolism, and it can harm cells when too much is produced.

A low HCO3- can also cause a low pH, but this not often seen in a baby right after birth.

Base Excess / Base Deficit

Base deficit (a negative base excess) is defined as the amount of strong base that must be added to return the pH to normal.  Thus, the more negative a BE, the more metabolic components there were that contributed to the acidic or low pH.  The more abnormally negative the base excess, or the larger the base deficit, the more serious the acidosis.  The greater the acidosis, the more serious the oxygen deprivation was in the baby, in most cases.  Although anything more negative than -8 is considered an abnormally low BE, most research shows that a BE equal to or more negative than -12 (or BD of 12 or more) is a predictor of complications in the newborn.

As mentioned earlier, a normal BE / BD and pH do not rule out the fact that the baby experienced oxygen deprivation before or during delivery.  There are a number or reasons a baby may have a normal BE and pH but still have experienced birth asphyxia.  For example, a baby may have suffered a very severe – even total – oxygen depriving event right before birth, which can occur in cases of complete placental abruption and complete umbilical cord occlusion.  In these instances, there may not have been enough time for the cardiopulmonary system to reflect the oxygen deprivation that occurred, yet the deprivation could have been severe enough to cause brain injury.  In other instances, the baby’s circulation and blood flow are so poor that the acid products that occurred due to anaerobic metabolism were not moving through the baby’s body via normal circulation and blood flow and therefore would not be reflected in the umbilical cord arterial blood gas sample.


There are many complications that can occur during or near the time of birth that, if mismanaged, can cause the baby to be deprived of oxygen.  During labor and delivery, the baby’s heart rate should be closely monitored with a fetal heart monitor.  If the baby starts to experience oxygen deprivation, non-reassuring heart tracings will appear on the fetal heart monitor.  When these tracings occur, the baby must be delivered immediately by emergency C-section delivery, in most cases.  Permanent brain injury from oxygen deprivation often occurs when non-reassuring heart tracings and fetal distress are not promptly acted on and the baby is left in oxygen-depriving conditions for too long.  Listed below are some complications that can occur shortly before or during delivery that can cause a baby to experience a lack of oxygen to her brain.

Pregnancy, Labor & Delivery Events that Can Cause Oxygen Deprivation in a Baby


Hypoxic ischemic encephalopathy (HIE) is a form of brain injury caused by oxygen deprivation.  HIE can cause the child to have lifelong problems, such as cerebral palsy, seizures, intellectual disabilities and developmental delays.  There is a treatment that can be given to a baby who has HIE, but it must be given within 6 hours of the insult that caused the HIE, which usually means it must be given within 6 hours of birth.  This treatment is called hypothermia (brain cooling) treatment, and it has been shown to halt almost every injurious process that starts to occur when a baby suffers an insult that causes HIE.  Research shows that hypothermia treatment can prevent death and cerebral palsy, and it can decrease the severity of the CP.


Just because a baby has abnormal umbilical cord blood gas results does not mean she will have permanent brain injury and lifelong conditions such as cerebral palsy, seizures, intellectual disabilities and developmental delays.  If the baby has HIE, early intervention in the form of hypothermia treatment may help prevent long-term problems.  In addition, prompt and appropriate resuscitation at birth (if necessary), proper management of the baby’s breathing, heart rate, blood pressure and circulatory issues, and timely treatment of seizures, hypoglycemia, jaundice and other neonatal problems can militate against long-term problems.


Michigan birth injury attorneys - Jesse Reiter and Rebecca WalshIf your baby was born prematurely and has a birth injury such as hypoxic ischemic encephalopathy (HIE), cerebral palsy, a seizure disorder or periventricular leukomalacia (PVL), contact the award winning birth injury lawyers at Reiter & Walsh ABC Law Centers.  Our firm is unique in that we focus solely on birth injury law and have been practicing in this area for almost 3 decades.  Reiter & Walsh ABC Law Centers is currently recognized as being one of the best medical malpractice law firms in the nation by U.S. News and World Report, and the partners of the firm, Jesse Reiter and Rebecca Walsh, were recently recognized as being two of the best medical malpractice lawyers in America by U.S. News and World Report.  In fact, U.S. News and World Report has given Jesse the honor of being one of the “Best Lawyers in America” every year since 2008.  The lawyers at ABC Law Centers have won numerous awards for their advocacy of children and are members of the Birth Trauma Litigation Group (BTLG) and the Michigan Association for Justice (MAJ).

If your child was diagnosed with a birth injury, the nationally recognized birth injury lawyers at ABC Law Centers can help.  We have helped children throughout the country obtain compensation for lifelong treatment, therapy and a secure future, and we give personal attention to each child and family we represent. Our birth injury firm has numerous multi-million dollar verdicts and settlements that attest to our success and no fees are ever paid to our firm until we win your case.  Email or call Reiter & Walsh ABC Law Centers at 888-419-2229 for a free case evaluation.  Our firm’s award-winning birth injury lawyers are available 24 / 7 to speak with you.