Ottawa researchers have found between 14 and 31 per cent of extremely premature infants, born between 22 and 25 weeks gestation, have severe developmental problems by the ages of four to eight.
The research took data pooled from more than 700 children who were born extremely prematurely to have the best estimate to date for the risk of certain developmental problems in this group.
The research is published in JAMA Pediatrics by Dr. Gregory Moore and colleagues from the Ottawa Hospital Research Institute, the Children’s Hospital of Eastern Ontario Research Institute and the University of Ottawa.
Severe developmental problems are defined as having at least one of the following characteristics: an IQ more than three standard deviations below the mean, cerebral palsy without the ability to walk independently, no useful vision or no useful hearing.
There was no significant difference in the percentage of children having severe developmental problems whether they were born at 22, 23, 24 or 25 weeks gestation.
Decrease in developmental problems with each extra week of gestation
However, there was a six per cent decrease in developmental problems with each extra week of gestation when moderate developmental problems were included in the analysis.
There were fewer surviving children at 22 and 23 weeks’ gestation so that data has been considered less reliable.
In a press release issued on Monday, Moore, a neonatologist at The Ottawa Hospital and CHEO, and an assistant professor at the University of Ottawa, said doctors have not been able to provide expectations to parents with babies born extremely premature, until now.
"This new data is not perfect, but the data and discussion about its limitations will give parents a much better picture than they had before of what to expect and consider when making decisions with their physicians and medical team about the care for their baby," said Moore.
"Of course, it is important for parents to remember that every baby is different, and it is impossible to predict how one will develop," he said.
To come up with the new estimates, researchers analyzed data from 738 children from nine studies in Europe, Australia, New Zealand and the United Kingdom, all conducted after 2004.
Studies from North America were not included because they did not fit the desired high-quality criteria.
All the studies had detailed birth records linked with cognitive testing of the same children between ages four and eight years.