What blood test can be used to determine whether brain damage was caused by lack of oxygen during birth?

Birth asphyxia occurs when a baby does not receive enough oxygen before, during or just after birth.  When asphyxia occurs during the delivery of a baby, depending on the duration of the oxygen deficit, a possible catastrophic chain of events occurs.  The balance of the baby's pH and blood gas levels may be altered by the birth asphyxia, putting the baby at risk for brain damaging acidosis.

Birth asphyxia may lead to increased PCO2 (carbon dioxide) and other gases in the blood, triggering decreased pH and leading to acidosis. Fetal asphyxia with acidosis can result in severe neurological injury, including cerebral palsy.

Cord blood is blood drawn from the placenta after delivery and is drawn from one of two umbilical arteries after the baby's delivery. The umbilical artery is where the baby's venous circulation delivers unoxygenated blood back to the mother.  This is blood that is on its way back to the mother's heart and lungs to pick up oxygen. A cord blood gas study is not drawn unless a baby is born with a low Apgar score within 5 minutes of delivery and birth asphyxia is suspected.

Blood from the umbilical artery is called a Cord Arterial Blood Gas (CABG) and basically shows how the baby was doing prior to birth. From this blood, the physicians are checking for acidosis. Acidosis is the metabolic condition that increases acidity.

If the pH is below 7.10, we know that the baby was hypoxic, or lacked sufficient oxygen, during the delivery. A pH level lower than 7.10 in the cord blood proves that the lack of oxygen to the baby occurred during the delivery and the hypoxic event was acute. Some experts believe that a pH of 7.0 or lower is an even more significant sign of asphyxia at birth, and this may lead to significant neurological dysfunction during life, or possibly even death.

A cord pH level of 7.10 or lower is an important component in determining whether birth asphyxia, or hypoxia, caused brain damage just prior to the delivery of the baby.