A controversial former midwife has pleaded not guilty to two counts of manslaughter in relation to the deaths of two babies during home births.

South Australian woman Lisa Barrett appeared in Adelaide Magistrates Court today over the deaths of Tully Kavanagh in October 2011 and another baby, who can't be named, in December 2012.

The two deaths were declared major crimes by police in 2013, with prosecutors alleging Ms Barrett failed to properly supervise the births.

The controversial homebirth advocate has pleaded not guilty to manslaughter. Picture: AAP (AAP)

In the first prosecution of its kind, Ms Barrett was last year granted bail on the condition she not approach witnesses in the case, not engage in any activities associated with home birthing and not be present at any birth.

The former midwife's lawyers this month abandoned a bid to have key prosecution evidence thrown out before trial, or to have the whole case abandoned.

Prosecutors have indicated up to 40 witnesses could be called at a trial.

After an inquest in 2012, South Australian Deputy Coroner Anthony Schapel found that Tully Kavanagh, the second of twins his mother planned to have at home, would have survived had he been delivered in a hospital.

Lisa Barrett, 50, was last year charged with the deaths of two babies during high-risk homebirths. Picture: AAP (AAP)

He made similar findings in relation to the deaths of two other babies who died during home births in which Ms Barrett was involved.

Those two other births are not the subject of any charges.

Magistrate Elizabeth Sheppard continued Ms Barrett's bail and committed her to the Supreme Court for arraignment in June.