A parliamentary inquiry into forced adoptions has heard how unmarried mothers were tied to beds and sedated as they gave birth.

Christine Cole gave birth to a baby girl at Crown Street Women's Hospital in Sydney in 1969.

She has studied forced adoptions for a PhD and believes many Australians are not aware of the practices the authorities used to carry out.

"Mothers were being tied to beds or drugged or had pillows or sheets held in front of their face so they couldn't see the baby at the birth - that was kept from the public," she said.

Another woman, Judy McPherson, told the Senate committee she remembered being sedated and waking semi-conscious in Melbourne's Queen Victoria Hospital when she gave birth as a 19-year-old.

She had been moved from her family home in Sydney to a Catholic centre for mainly unmarried mothers in Carlton and was told she needed a false name.

"My daughter was born in Queen Victoria Maternity Hospital in Melbourne in November 1964 and I first met her in 1990," she said.

Sorry, this audio has expired Senate inquiry hears harrowing evidence on forced adoptions ( Sabra Lane )

Ms McPherson broke down near the start of her submission and the rest had to be read by someone else on her behalf.

The women want the history of any Commonwealth involvement in the process documented.