Importance of Interpreting Umbilical Cord Blood Gases in Newborns

At the moment of birth, the most objective method of assessing a newborn’s metabolic condition is by analyzing umbilical cord blood gas. To be specific, arterial cord pH and base deficit can determine perinatal hypoxia and be an insight into causes of fetal distress.

Umbilical cord blood gases are most likely interpreted in situations of high risk pregnancies when there are abnormal fetal heart rate patterns, when there is an intrapartum fever, emergent C-section for a fetal compromised, low Apgar scores (less than 3) or when there are multiple fetal births.

There are three most common causes of neonates hypoxia or asphyxia, which are when the mother is oxygen compromised, when there is preeclampsia, chronic hypertension, hypotension, hypovolemia or cyanotic heart disease. Another type of condition that causes hypoxia or asphyxia is when the oxygen flow from the placenta to the fetus is obstructed or impaired. This could be caused by a placental abruption, a cord prolapse, or repetitive cord blockage.

To obtain a sample of umbilical cord blood, a 10-20 cm section of the umbilical cord is double-clamped and put on ice. The assessment should take place within 60 minutes.

Umbilical cord blood analysis is designed to give a picture of the acid-based balance of the infant at the moment of birth. Right after the baby is delivered, the umbilical cord is clamped. From that moment on, the umbilical cord blood, if it remains in the placenta, will show the progressive change in acid-base status due to the ongoing placental metabolism and gas exchange.

Small changes in umbilical pH occur within 60 seconds of delivery; over 60 minutes, cord arterial or venous pH can fall by more than 0.2 pH units. These changes are not observed if the cord is doubly clamped at birth.

When there is a delay in sampling of the umbilical cord, it is important to know whether the sample is taken from isolated cord blood or whether ongoing placental metabolism may have altered the results. The umbilical cord can become obstructed before birth. The restriction of umbilical blood flow causes aggressive widening of the differences between the umbilical arterial and venous blood gas values.

The pH of umbilical cord blood is determined by the presence of respiratory and metabolic acids. Carbon dioxide diffuses readily across the placenta.

In addition, the blood gas analysis measures pH, PC02 and P02 and then calculates base excess after normalizing the PC02.The P02 and PC02 values can provide clues to the clinical condition of the newborn.

Umbilical cord blood gas analysis is suggested in all high-risk deliveries. It is performed routinely after all deliveries in some hospitals. For the best and most accurate interpretation of umbilical cord blood gases, umbilical arterial and venous samples should be taken soon after birth from the segment of the umbilical cord that has been doubly clamped or isolated from the placenta. Low cord pH in infants who are vigorous and active at birth and free of cardiopulmonary compromise does not indicate an increased risk of adverse outcomes. Infants with pH less than 7.0 at birth who are not active are at high risk of adverse outcomes. Identification of infants at risk of encephalopathy is especially important in the case where early intervention could save the child.

Birth injuries caused by oxygen deprivation to the fetus are extremely dangerous. Umbilical cord blood gases are essential in diagnosing hypoxic ischemic encephalopathy.
In the womb, the fetus does not breath in the same way humans do. The fetus depends on the mother for oxygen and carbon dioxide exchange. It is the placenta that connects the growing fetus to the uterine wall from which the fetus receives nutrients and gas exchange by way of the mother’s blood supply.

To determine if a newborn has suffered an oxygen-depriving event, doctors examine the umbilical artery blood because this is the blood that comes from the baby as opposed to the blood going to the baby through the umbilical veins. When the baby does not receive sufficient oxygen, permanent brain damage can lead to cerebral palsy and seizure disorders.

There are a number of different causes of fetal oxygen deprivation causing brain damage.

Reduced transfer of oxygen from the mother to the fetus can be caused by several placental complications, including placental abruption, placenta previa and a placental infection.

The interpretation of umbilical cord blood gases is often used in birth trauma lawsuits. In many birth trauma injury cases, the obstetrician and hospital may defend the case by claiming normal cord gases even though the fetus suffered from oxygen deprivation or asphyxia or hypoxia. It is critically important that the analysis of the umbilical cord blood gases be shown to be accurate by demonstrating that the blood was drawn from the correct vessel and that it was stored properly. Obstetricians and hospitals who have been named as responsible parties for the brain injury to a newborn will often defend by trying to invalidate the umbilical cord gas results. They may claim that the umbilical cord gases were invalid because of a technical error or because the blood was drawn from the wrong vessel or that the brain injury was caused by some other superseding event.

Kreisman Law Offices has been handling birth trauma injury cases, traumatic brain injury cases, newborn death cases and wrongful death cases for individuals, families and loved ones who have been injured, harmed or killed as a result of the negligence of a medical provider for more than 40 years, in and around Chicago, Cook County and surrounding areas, including Tinley Park, River Grove, Elmhurst, Elk Grove Village, Countryside, Country Club Hills, Vernon Hills, Oak Lawn, Park Forest, Palos Hills, Palatine, Lemont and Lake Forest, Ill.