Ireland goes to the polls on Friday for a referendum on liberalising one of Europe's strictest abortion regimes.
Voters will decide whether to repeal the Eighth Amendment of the constitution which prohibits terminations unless a mother's life is in danger.
The result should be known on Saturday.
The Catholic church is among influential voices arguing the life of the unborn should be sacrosanct, but faces a major challenge from a yes camp which has portrayed itself as modernising and in step with international opinion.
If the public votes Yes the Irish Government intends to legislate by the end of the year to make it relatively easy for a woman to obtain the procedure in early pregnancy.
Ministers have promised to allow terminations within the first 12 weeks, subject to medical advice and a cooling-off period, and between 12 and 24 weeks in exceptional circumstances.
The debate during eight weeks of campaigning has been divisive, with the leaders of all the main political parties including Taoiseach Leo Varadkar lining up as self-styled women's rights advocates in backing change.
They argued a yes vote represented the compassionate choice for thousands of Irish women forced to travel to England for the procedure.
Opposing them was a vocal No camp including the bishops which believes the life of the child is sacrosanct and interference in that right immoral.
No campaigners have used emotive language to highlight the threat to the foetus and warned against "extreme" proposals from the Government which could be expanded in future years.
Opinion polls have been tight, with the indication rural voters are more likely to vote no than their urban counterparts and significant numbers of don't knows casting a degree of uncertainty about the result.
Around 2,000 voters in 12 islands off the mainland voted on Thursday to prevent any delay in counting their ballot papers.
The Eighth Amendment is a clause in the constitution which was written after a previous referendum on the issue in 1983 recognised the right to life of the unborn child.
It protects the equal right to life of the mother and the unborn and effectively prohibits abortion in most cases.
In 1992, women were officially given the right to travel abroad, mostly to the UK, to obtain terminations. Pro-repeal campaigners said almost 170,000 have done so.
The liberalisation campaign gathered momentum after an Indian dentist, Savita Halappanavar, died in hospital in Galway aged 31 when she was refused an abortion during a miscarriage.
Her husband, Praveen Halappanavar, said she repeatedly asked for a termination but was refused because there was a foetal heartbeat.
In 2013, legislation was amended to allow terminations under certain tightly restricted circumstances - the Protection of Life During Pregnancy Act.
When doctors felt a woman's life was at risk due to complications from the pregnancy, or from suicide, they were permitted to carry out an abortion.
Under pressure from the UN about alleged degrading treatment of women who travelled to England for terminations the Irish Government began exploring the possibility of further reform, culminating in the calling of this referendum and the promise to legislate.