Voters in Ireland are casting their ballots in a landmark referendum to decide whether to remove a constitutional amendment that bans abortion in almost all circumstances.

Polling stations across 40 constituencies opened at 7 a.m. local time. An electorate of around 3.2 million are eligible to cast their ballots, including thousands of Irish people living overseas who have flown home to vote. If the Yes campaign wins, Irish lawmakers are expected to enact legislation allowing for terminations in the first 12 weeks of pregnancy – and later in cases where there is a risk to the mother’s life or the fetus is not expected to survive.

A No vote would keep Ireland’s abortion laws – some of the strictest in the developed world – in place.

The Eighth Amendment, which was added into the constitution following a referendum in 1983, places the rights of the fetus and the rights of its mother on equal footing, effectively banning abortion barring a “real and substantial risk” to the mother’s life.

As with any proposed change to Ireland’s constitution, the question has to be put to a referendum.

Abortion-rights activists – advocating a Yes vote on Friday – have long argued that the Eighth Amendment punishes women and doesn’t stop abortions, which are exported, mostly to the UK, instead.

Their longstanding campaign to repeal the Eighth, as it is commonly known, has seen some change over the past three decades. In 1992, the X Case made it legal for Irish women to travel abroad for abortions, adding the threat of suicide as grounds for abortion. In 2013, Savita Halappanavar died of sepsis after being denied a termination of a miscarrying fetus in a Galway hospital, prompting the government to pass a bill allowing abortions when a woman’s life is in danger. And in June 2016, the UN’s Human Rights Council ruled that the country’s abortion regime subjected Amanda Mellet, a dual Irish-American national, to “cruel, inhuman and degrading treatment,” and called on the Irish government to reform its laws.

Throughout the years, Ireland’s abortion-rights campaigners have mobilized en masse, with demonstrations that have brought Dublin to a halt and found support across the globe.

Anti-abortion activists will be voting No, arguing that the Eighth has saved thousands of lives and encouraged compassionate alternatives to abortion, such as perinatal hospice care when the baby is not expected to survive or adoption for babies born to women in challenging circumstances. The No campaign has also found support from anti-abortion groups worldwide, including some American activists who have traveled to speak at rallies.

Polls will close at 10 p.m. local time on Friday. Counting of ballots will get underway on Saturday, with a result expected by mid-afternoon.

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