Cord blood gas analysis is a procedure that is used to assess the quantities of gases present in arterial as well as venous cord blood. It is a controversial procedure that has acquired importance in medico-legal context rather than in the medical field per se.

Basically cord blood gas analysis determines the level of oxygen and carbon dioxide present in the blood sample as well as the pH of the blood sample. The umbilical cord blood gas values are useful in determining if a newborn is depressed and has acidosis, which could lead to neurological complications in later life.

Measuring the gas values will also help in gauging if the baby is suffering perinatal asphyxia. The value of gas analysis of the cord blood was first stated by James et al. in 1958. The authors opined cord blood gas analysis could give an indication of preceding fetal hypoxic stress.

In simple words this means doctors are able to assess if the infant is deprived of oxygen immediately after birth. If the infant is indeed deprived of oxygen then emergency measures need to be taken to supply adequate oxygen, else there is every chance of development of permanent neurologic disability like cerebral palsy.

Normally the very first test given to newborns is the APGAR score. This test named after Dr Virginia Apgar, stands for Activity, Pulse, Grimace, Appearance, and Respiration. The test is given one minute after birth, and then after 5 minutes. The test assesses the health of the infant immediately after birth. Low scores indicate newborn depression or distress due to lack of adequate oxygen.

However recent studies advocate using cord blood gas analysis as a more accurate method of determining the status of an infant at birth.

The Royal College of Obstetricians and Gynecologists and the Royal College of Midwives in the UK advocate “routine measurement of cord blood gases for all caesarean sections or instrumental deliveries for fetal distress indication.”

A joint statement issued by them also states that “consideration should be given to measurement of cord blood gases following all deliveries. The presence of normal gases, but not pH alone, largely excludes hypoxia as a cause of brain damage and has important medico legal implications.”

The most recent American College of Obstetricians and Gynecologists Committee Opinion(#348) states, “Physicians should obtain arterial and venous cord gases in the following situations; Cesarean delivery for fetal compromise, low 5 minute Apgar, severe growth retardation, abnormal fetal heart rate tracing, maternal thyroid disease, intrapartum fever, multifetal gestation.”

The gases and other values that are measured in the analysis include: Oxygen pressure Carbon dioxide pressure Acid-base balance as measured by pHBicarbonate levels Base excess

A study by Dickinson et al, Obstetrics & Gynecology 1992;79:575-578, concluded, “Because umbilical cord gas indices are an objective means of assessing the immediate status of the newborn, they may be of more value in excluding birth asphyxia than is the Apgar score for pre-term infants.”

Nevertheless cord blood gas analysis continues to be a controversial procedure in the medico-legal field. Doctors these days are encouraged to use this procedure in order to maintain accurate records of the health of the baby immediately after birth.