People who want to terminate their pregnancy after 28 weeks could be required to instead deliver their baby alive under proposed changes to laws in South Australia that decriminalised abortion three years ago.

Liberal MP Ben Hood will introduce a bill in the SA upper house on Wednesday so that people pregnant for more than 27 weeks and six days would be induced instead of getting an abortion.

Under SA legislation passed in 2021, a pregnant person can get a late-term abortion after 22 weeks and six days if medically appropriate and with the approval of two doctors.

"What my amendments hope to do, is balance the choice of the mother with the rights of the child," Mr Hood said.

"This importantly balances and does not impinge upon the rights of a mother to choose a termination.

Mr Hood said the "unintended consequences" of the current legislation were 45 babies being aborted after 22 weeks and six days over an 18-month period.

The South Australian Abortion Reporting Committee reported eight late-term terminations in 2022 and 37 in 2023 because of a risk to the physical or mental health of the pregnant person.

In a statement, SA Health said that in the first 18 months after the current legislation was implemented, there were fewer than five terminations performed after 27 weeks and no terminations performed after 29 weeks.

SA Abortion Action Coalition's Brigid Coombe said she was disappointed with Mr Hood's proposed amendments.

"Those changes remove the basis of informed consent and they don't recognise at all the complexity of the circumstances that people are in when they need an abortion at those gestations," she said.

"It is not an uncommon feature – people who are opposed to abortion or want to paint women in a light that is practically misogynistic, that these bills would be brought forward."

Ms Coombe said the coalition has always placed importance on the person who is pregnant.

"You can't say that you're going to force somebody to do something against their will [and] at the same time say, 'That you're going to find that balance between choice,'" she said.

"It disregards all the very serious decision-making that goes into these circumstances, and really makes light of it."

In 2021, the historic bill that moved abortion from the Criminal Law Consolidation Act into healthcare legislation passed parliament after members of parliament were granted a conscience vote.

The changes brought South Australia into line with most jurisdictions in the country, with then attorney-general Vickie Chapman stating the move was about "giving women choice".

Currently, late-term abortions will only be approved if there is a threat to the life of the pregnant person or another fetus, or if there is a significant risk of serious fetal anomalies associated with the pregnancy.

Terminations will also be approved if the continuation of the pregnancy would involve a significant risk of injury to the physical or mental health of the pregnant person.

University of Adelaide Professor of Law Joanna Howe said the proposed changes do not infringe on women's rights.

"[The bill] allows termination of pregnancy throughout all nine months, all it does is after 28 weeks, the baby is delivered alive rather than stillborn," she said.

"At that point, they are treated like any other South Australian baby who's born prematurely … if the baby is not going to survive because they've got a condition like anencephaly, the palliative care would be given to that child and they would be made comfortable until they passed.

"But if that baby is healthy … they'd be rushed to the NICU, they'd be given life-sustaining treatment and they would survive.

"Unless the pro-choice mantra is 'my baby, my choice', I don't think you can mount a pro-choice argument against this bill."