EVEN a relatively mild lack of oxygen around birth can be linked to long-term effects on a child's development, according to new research.
It means that at-risk children should be monitored for learning and behavioural difficulties, the study from University College Cork found.
It examined the newborns who had experienced hypoxic-ischaemic encephalopathy, or HIE, in which the baby's brain lacks oxygen around the time of birth.
It affects around three in every 1,000 babies born in Ireland. It is a leading cause of neonatal death and survivors are at risk of a variety of disabilities, including cerebral palsy, epilepsy and intellectual disability.
Prof Geraldine Boylan and Health Research Board clinician scientist Dr Deirdre Murray recorded EEG or 'brain waves' of 60 babies with HIE and found that even where the HIE was relatively mild, in some cases it was linked with developmental delays as long as five years later.
Prof Boylan explained: "Most previous research has indicated that only infants with moderate or severe HIE experienced long-term difficulties."
She said that using EEG measurements to assess HIE within hours of birth and then following up with those children over five years, she found that subtle learning deficits were common following both moderate and mild HIE.
The study showed 18-20pc of infants who had mild HIE at birth had learning or behavioural difficulties at five years, including speech delay, autism, attention deficit disorder and dyspraxia.
Both moderate and mild cases of HIE were linked with overall blunted IQ scores, decreased processing speeds and poor working memory.
"Infants with moderate HIE are currently offered therapeutic hypothermia (brain cooling) to help address the condition.
"But infants with mild HIE are not. This is due to the previously held perception that mild HIE has no long-term consequences, but our work is showing that some children who experience mild HIE could benefit from repeated follow up and assessment during early childhood."
Therapeutic hypothermia is a possible treatment for brain-damaged babies or babies who lacked oxygen at birth.
The treatment is termed therapeutic cooling and it involves cooling the newborn to 32 degrees centigrade for 72 hours as soon as possible after birth.
The reasons behind it working is not fully understood, but it may be that cooling slows down chemical reactions, and gives the repair mechanisms found inside cells a chance to get to work without being overwhelmed.
As soon as possible after birth, and with strict controls in place, the baby is cooled with a special cap or with a special blanket or mattress.
After about three days, the baby is gradually warmed again.