Nearly 1 in 5 Aboriginal children born in Western Australia has no birth documents with most unregistered children born to teenage mothers and facing further social disadvantage later in life, research showed on Sunday.

A study published in The Australian and New Zealand Journal of Public Health matched data from the state's midwife records against the birth registry office, and found that 18 percent of Aborigine children did not have birth certificates.

Between 1980 and 2010, there were nearly 50,000 aboriginal births in Western Australia, and of that number, 4,628 children under 16 were not recorded at birth.