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A new predictor of newborn health: Umbilical cord blood pH

May 14, 2010 |  3:53 pm

High acidity of blood in the umbilical cord at birth is a good predictor of cerebral palsy, brain damage and death in childhood, researchers said Friday. Researchers had suspected that acidity of the blood, as measured by pH, was linked to such adverse outcomes, but previous studies have not been definitive. The new findings suggest that a broader use of pH monitoring for newborns might provide a better picture of those who will need closer monitoring throughout infancy, Dr. James P. Neilson  of the University of Liverpool said in an editorial accompanying the report in the journal BMJ.

pH is a measure of acidity in liquids. A pH of 7 indicates neutrality, pHs from 7 to 1 indicate increasing acidity and pHs from 7 to 14 indicate increasingly alkaline conditions. Umbilical cord blood should be very close to pH 7, but some complications of childbirth can lower it. If the umbilical cord is compressed, for example, limiting the amount of oxygen the infant receives, the infant's body will produce more lactic acid in response and the umbilical cord pH will be lowered. Oxygen deprivation during labor is the most common cause of brain damage and premature or very small infants are at the highest risk.

In the new study, Dr. Gemma Malin of the University of Birmingham and her colleagues combined results from 51 studies of low umbilical cord pH covering almost half a million children. They reported that the individual studies were widely varying in quality and approach, but that the results were similar no matter how the studies were conducted: a strong and consistent association with infant death, brain damage and cerebral palsy. They found that a low pH in arterial blood from the umbilical cord was associated with a 17-fold increase in fetal mortality, a 14-fold increase in encephalopathy or brain damage and a 2.3-fold increase in cerebral palsy.

Umbilical cord pH is frequently monitored at birth if physicians suspect that the infant was oxygen deprived. The results suggest that it could be used more widely as a safety precaution to predict which infants might be at increased risk. Measuring pH is a simple task. The only potential difficulty is isolating it from the umbilical cord. In many cases, the researchers said, the cord is clamped off too soon, giving an inaccurate picture of actual pH.

-- Thomas H. Maugh II

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