The number of NSW teenagers taking their own lives has jumped to its highest point in 19 years.
At the same time, deaths from road accidents - which used to be the leading killer for 15-17 year olds - has been gradually declining, according to figures in the NSW Child Death Review Team's (CDRT) 2015 report.
Overall, 504 children died in 2015 from all causes - the lowest the rate has been since 1996.
But 58 per cent of those children were infants aged less than 12 months and 42 of them died suddenly and unexpectedly.
Acting NSW Ombudsman John McMillan said "there are still too many preventable deaths".
"The decline is not uniform," Professor McMillan said as the report was tabled to parliament on Tuesday.
Children from Aboriginal and Torres Strait Islander backgrounds continue to be more at risk of death, with their mortality rate 2.3 times higher than non-indigenous children.
Almost all of the infants who died were exposed to one or more known risk factors such as placing an infant to sleep on their front or sharing a bed with them, particularly while alcohol or drug-affected, Prof McMillan said.
The report said safe sleeping advice should include strategies to avoid unintentional bed sharing, particularly for disadvantaged and vulnerable families.
For children aged between 1-4 years, the report found drowning was the second leading cause of death, after congenital and chromosomal conditions.
In a separate review, the CDRT also looked at children's deaths from vaccine preventable infectious diseases.
It found that 23 deaths between 2005 and 2014 were preventable or potentially preventable by vaccination, with influenza and meningococcal the most common causes.
The report's findings highlight that immunisation has been successful in dramatically reducing the number of child deaths from infectious diseases, Prof McMillan said.
Kids Helpline 1800 55 1800 (for young people aged 5 to 25).
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