The Commission of Investigation's final report into Mother and Baby Homes will be brought to Cabinet later.
It's expected to show 9,000 children died in the institutions - around 1 in 7 of the babies born there.
The commission was set up in 2015 following claims the bodies of 796 babies lay in an unmarked grave at the Bon Secours Mother and Baby Home in Tuam.
The investigation looked at 18 homes, including Tuam and Bessborough in Cork, and is expected to show 9,000 children died in the institutions between 1922 and 1998.
Details seen by the Sunday Independent, show the mortality rate - at 16 percent - was four times that of the general population.
Survivors have expressed their frustration at the leaking of the report, which the Children's Minister has said will be investigated.
The entire 4,000 pages will be published this afternoon, after being discussed at Cabinet and presented to survivors.
The Taoiseach will make a State apology to survivors in the Dail tomorrow.