Liberal MP Ben Hood's private member's bill would have required women wanting to terminate their pregnancy after 28 weeks to deliver their baby alive.
Liberal Michelle Lensink opposed the reforms but is on leave while she fights breast cancer.
The Advertiser reported that she had been "paired" with fellow Liberal Jing Lee, who spoke in favour of the bill during the debate on Wednesday night.
South Australian Liberal Michelle Lensink is on leave while she fights breast cancer. (David Mariuz/AAP PHOTOS)
Under pairing arrangements, MPs who are on leave are paired with MPs who sit the vote out to ensure the absence does not affect the final result.
However, The Advertiser reported that Ms Lee opted out of the pair arrangement late on Wednesday night which would have levelled the vote at 10-10.
That would have left Legislative Council President Terry Stephens - a conservative Liberal - to cast the deciding vote.
As the debate was concluding, Labor MP Russell Wortley filibustered while Ms Lensink and her young son caught an Uber to Parliament so she could vote.
"Tonight was a wild ride, which had nothing to do with the Uber drivers," she wrote on X.
At the last minute, Liberal Dennis Hood agreed to sit the vote out as her pair and the bill was defeated 10-9.
In a subsequent post on X, Ms Lensink wrote: "I don't understand what happened tonight, but as someone who thought they had a pair from parliament, I had One Nation's Sarah Game lie to me on the phone that she would pair me on the termination laws. It shows how desperate (and un-Australian) some people are in this debate."
Ms Game told The Advertiser said she never committed to be Ms Lensink's pair and felt there had been a misunderstanding between them.
"On a conscience vote and on a vote that was so significant for me and my constituents, I couldn't be that person to her," she said.
I don't understand what happened tonight, but as someone who thought they had a pair from parliament, I had One Nation's Sarah Game lie to me on the phone that she would pair me on the termination laws. It shows how desperate (and un-Australian) some people are in this debate— Michelle Lensink (@miclensink) October 16, 2024
SA's abortion laws, which passed parliament on a conscience vote in 2021 under the former Marshall Liberal government, set out conditions for "terminations by medical practitioner after 22 weeks and six days".
Mr Hood's bill proposed that in cases where pregnant women seek a termination of a child after 28 weeks, they could end their pregnancy through early delivery, allowing the baby to receive medical care and have the chance to live.
A demonstration against the bill outside parliament on Wednesday attracted about 100 chanting protesters.
It included eight women dressed as handmaids, inspired by Margaret Atwood's novel The Handmaid's Tale.
SA Director of the Australian Christian Lobby, Ashlyn Vice, said the outcome was devastating.
"Tonight's result means more South Australian babies will be needlessly born dead when they could have been safely born alive," she said.
Reproductive rights have been thrust into the spotlight across Australia. (Abe Maddison/AAP PHOTOS)
But the SA Abortion Action Coalition said the vote reaffirmed the parliament's commitment to abortion healthcare and reinforces the status of abortion as decriminalised across all Australian jurisdictions.
"The Coalition is relieved to be able to refocus our attention on improving pathways to quality healthcare for those seeking later abortions due to extremely challenging circumstances, and to supporting those involved in this care," it said in a statement.
More than 1000 people who support the bill gathered on the steps of parliament in September.