The truth is far more complex, according to an important new report by a committee of experts in obstetrics, pediatrics, neurology and fetal-maternal medicine. Many conditions that occur during or even before pregnancy can lead to neurological damage to full-term babies.
The document, called Neonatal Encephalopathy and Neurologic Outcome, updates a version published in 2003 that focused on oxygen deprivation, or asphyxia, around the time of birth. The new report highlights significant advances in diagnosis and treatment.
According to the 2003 report, fewer than 10 percent of children with cerebral palsy, the most severe such brain injury, showed signs of asphyxia at birth. Unless certain clear-cut symptoms are present then, brain abnormalities are probably not the result of a complication during labour or delivery, the new report states.
Rather, there may be other reasons for neonatal encephalopathy, as brain disorders in full-term newborns are called. These include genetic factors and maternal health problems like hypothyroidism, placental abnormalities, major bleeding during pregnancy, infection of the foetal membranes and a stroke in the baby around the time of birth.
To determine whether an insufficient supply of oxygen and blood during labour and delivery is the likely cause, several factors should be considered together. These include a low Apgar score at 5 and 10 minutes after birth; high acid level (called acidemia) in the umbilical artery; major organ failure; and an MRI scan showing a particular pattern of cerebral injury, according to the new report. The more of these conditions that are present, the more likely that insufficient oxygen during the birth was responsible for the injury.
The experts noted that there are multiple potential causal pathways that lead to cerebral palsy in term infants, and the signs and symptoms of neonatal encephalopathy may range from mild to severe, depending on the nature and timing of the brain injury.
For example, the injury might occur as a result of risk factors at the time of conception or from conditions that develop during pregnancy, like fetal growth retardation or placental lesions.
JANE E BRODY