Clear association between cerebral palsy and low Apgar score
Cerebral palsy (CP) is the most common neurological disability in children, and is diagnosed in approximately two children per thousand in Western countries. A strong correlation between the Apgar score and CP in children with normal birth weight has previously been seen, although such a relationship has been uncertain in children with low birth weight. A 2010 study from the Norwegian Institute of Public Health showed a clear association between CP and Apgar score in children with both normal and low birth weight. The results were published in the British Medical Journal.
“In all birth weight groups, we found that between 10 and 17 per cent of children with a very low Apgar score developed cerebral palsy. It is important to be aware of this when following the progress of these children. At the same time, I would emphasise that more than 80 per cent of children did not develop cerebral palsy," said physician and researcher Kari Kveim Lie at the NIPH.
What is the Apgar score?
The Apgar score is a system to measure the vitality of a newborn child, based on the evaluation of heart rate, respiration, skin colour (pink or pale, blue), muscle tone and reflex irritability. The Apgar score is recorded for all newborns, whether they are born in a small delivery room or in a specialised unit with advanced technical birth monitoring. An Apgar score of 7-10 is considered normal, 4-6 is low, and below four is very low.
The study examined the association between Apgar score, birth weight and cerebral palsy using a research database of children with cerebral palsy born in the period 1986-95. The register was linked to the Medical Birth Registry of Norway, which contains information on birth weight and Apgar score.
The results show that among children with normal birth weight (2500 grams and higher), the incidence of CP is more than 100 times greater in children with a very low Apgar score compared with children with a high Apgar score. Ten per cent of newborns with an Apgar score lower than 4 developed cerebral palsy, compared with only 0.1 per cent among children who scored above 8.
In the group with the lowest birth weight (under 1500 grams), 17 per cent of the children with an Apgar score lower than 4 developed cerebral palsy compared to four per cent of newborns with an Apgar score over 8.
Interpretation of results
A low Apgar score may indicate that the child received too little oxygen during birth, but it can also be caused by other factors that impair the vitality of the child. If the child's nervous system has a reduced function, it can affect all components of the Apgar score. Thus, a low Apgar score can also be considered to be a sign of actual brain damage that causes cerebral palsy; a brain injury that could just as easily have occurred during pregnancy as in birth. This study cannot determine to what extent cerebral palsy is due to birth-related brain damage compared to damage that has occurred previously.
What is cerebral palsy?
Cerebral palsy is a disability caused by a brain injury that occurs while the brain is immature, i.e., in the uterus, during birth or during the first months of life. The diagnosis is made on the basis of clinical examination, and is not based on either laboratory tests or specific anatomical changes. It was previously believed that injury associated with birth was the most frequent cause of cerebral palsy, but recent research suggests that most cases are due to conditions before birth. The cause of cerebral palsy in the individual child is, in most cases unknown.