Dublin voter Helen, 47, who did not want to give her surname and is now unemployed after suffering cancer, said her radiation treatment would have been stopped had she been pregnant, under existing laws giving equal right to life to expectant mothers and unborn babies. The government's vote count begins at 9 a.m. on Saturday in Dublin. They called it a once-in-a-generation opportunity to liberalize some of Europe's strictest abortion rules.
Al Jazeera's Neave Barker, reporting from Ireland, said the vote had split Irish society between those in favour of repealing the abortion ban and those who wish to see it maintained.
Sky's senior Ireland correspondent David Blevins said it was a wider margin than many people in the Catholic country had expected.
It's 35 years since the Eighth Amendment was inserted into our constitution.
Thousands of Irish people overseas travelled home to take part in the historic referendum, and supporters of repeal gathered at Dublin Airport to give arrivals an ecstatic welcome. Many Irish residents living overseas have flown home to vote on both sides.
They argue that the right to life of the unborn child which the 1983 vote equated to that of the mother is a human rights issue.
However, campaign group Save The 8th says politicians are "effectively seeking a licence to kill pre-born babies, and to introduce an abortion model that is in many ways even more extreme than the British regime".
The newspaper exit poll indicated overwhelming support for change.
"If the referendum doesn't pass these women will continue to have to travel overseas in their thousands".
But no social issue has divided its 4.8 million people as sharply as abortion, which was pushed up the political agenda by the death in 2012 of a 31-year-old Indian immigrant from a septic miscarriage after she was refused a termination.
"A high turnout I think would be to the advantage to the "yes" campaign, and obviously the upside of a good sunny day in Ireland is that people come out to vote".
Chris Garvin, 20, who works in human resources, said: "I'm not going to try and sway people's opinions but it's a very, very important matter and I think it's going to affect everybody's lives in some way".
It says that "the state acknowledges the right to life of the unborn and, with due regard to the equal right to life of the mother, guarantees in its laws to respect, and, as far as practicable, by its laws to defend and vindicate that right".
The voting took place on a day that was sunny throughout much of Ireland, which may have bolstered turnout.
"It's not a vote on me, not a vote on the government", Varadkar said this week in Dublin, according to the Financial Times.
The ballot paper does not mention the Eighth Amendment or abortion, instead asking: "Do you approve of the proposal to amend the Constitution contained in the undermentioned Bill?"
In the region of 120,000 people have added their name to the supplementary voting register in recent weeks and thousands of people have travelled home from overseas to cast their votes.