If passed, the bill would then go before the Senate, where it faces an uphill battle to become law. The new bill would decriminalise abortion during the first 14 weeks of pregnancy, and even afterwards conditionally.
Lawmakers in Pope Francis' native Argentina vote on Wednesday on legalising abortion, which if passed, would make it the most populous country in South America to allow women to terminate pregnancies.
The debate has divided Argentinian society. Though it has shed some of its traditionalism by pioneering the legalisation of gay marriage in Latin America, it remains strongly influenced by the Catholic Church.
The Chamber of Deputies is deeply divided over the issue and after weeks of bitter debate, the result of Wednesday night's vote is far from certain.
Of the Chamber's 257 deputies, 109 are expected to vote in favor of the bill, 117 against, with the remaining 29 undecided lawmakers casting the decisive votes in the lower house.
"Today we see an almost a neck-and-neck vote, with a slight advantage for those against the bill," said Martin Maquieyra of President Mauricio Macri's ruling Cambiemos party, who will vote against.
Pro- and anti-abortion groups have called for demonstrations outside Congress on Wednesday.
As in most Latin American countries, abortion is illegal in Argentina, except in cases of rape or when the life or health of the woman is at risk.
The new bill would decriminalise abortion during the first 14 weeks of pregnancy, and even afterwards in cases where the foetus suffers from conditions not compatible with life outside the womb.
If passed, the bill would then go before the Senate, where it faces an uphill battle to become law. Analysts point out that more senators have spoken out against the bill than in its favour.
Macri, who has come out strongly against abortion, has asked lawmakers to vote with their conscience, and said he would not veto the bill if passed.
"We hope that the respect is maintained, we are all Argentines, we can have very different ideas, but with respect," said pro-government deputy Daniel Lipovetzky.
Not One Less
Once considered highly unlikely in traditionally Catholic, conservative Argentina, support for decriminalising abortion has grown in recent years, boosted by a vociferous #NiUnaMenos (Not One Less) campaign against violence against women as well as by last month's referendum legalising abortion in Ireland.
That momentum has set it on a collision course against the religious right, determined to block the legalisation of abortion, a war being fought on the pope's turf.
In March, as the abortion debate heated up, the former Buenos Aires archbishop sent a letter to the Argentine Episcopal Conference asking them to "make a contribution in defence of life and justice."
Supporters of the bill have denounced church pressure.
"It complicates things ... But if abortion has been legalised in Italy, where the power of the church resides, I don't see why this would represent a greater difficulty in Argentina," said sociologist Sol Prieto from the University of Buenos Aires.
"The church no longer has a monopoly, the religious dynamic is changing in recent times in Argentina," said Prieto.
Deaths due to abortion
According to official health ministry statistics, over 17 percent of the 245 recorded deaths of pregnant women and girls in 2016 were due to abortion.
NGOs say some 500,000 abortions a year are carried out clandestinely, often in conditions that pose a health risk for women and girls.
"We are not questioning the personal and religious beliefs of the legislators, we are debating whether clandestine abortion is going to continue or whether the state is going to guarantee legal abortion, so there will not be one more dead," said activist Myriam Bregman of the Workers' Left Front party.
Macri's vice president, Gabriela Michetti, has come out strongly against the bill.
"Being in favour of life is much more progressive and respectful," she said.
"If a woman does not want to be a mother, whatever the motive, she can entrust the child for adoption."
Whatever the outcome, the tide of public opinion is blowing in one direction, according to sociologist Prieto.
"I don't know if the law will be adopted, but if it's not voted in this time, it won't be long before it is. It's a movement that you can't stop."
Latin America has strict laws outlawing abortion, except in Uruguay, Cuba, Guyana and Mexico City, where it is legal.