LOS ANGELES – 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.

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.

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 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.