Update 3.08pm: One in five pregnancies could be terminated in Ireland next year if the country's strict abortion laws are changed after May's referendum, pro-life campaigners have claimed.
Activists urged voters to join a "rebellion" against the country's "elites" in voting No as they officially launched their Save the 8th campaign.
Young children and TDs were among a crowd gathered in Dublin at the event where speakers included medical professionals, students and mothers.
Citizens will be asked on May 25 whether they want to repeal the Eighth Amendment of Ireland's Constitution, a provision that makes abortion illegal in all but exceptional circumstances.
Voters will be asked whether they want to replace the Eighth Amendment, which gives the mother and unborn an equal right to life, with wording that hands responsibility for setting the country's abortion laws to politicians.
If the public votes to repeal the constitutional provision, the Irish Government intends to table legislation that would permit women to abort within 12 weeks of pregnancy.
Activists described a Yes vote in May's referendum as a "horrible and tragic mistake" and claimed it would be a "licence to kill" the unborn, at the campaign launch in the Gresham hotel today.
Caoimhe Lynch, from Killarney in Co Kerry, said her mother fell pregnant as a 23-year-old nursing student.
Ms Lynch, 20, told the crowd: "It was suggested to her that she should have an abortion. Now imagine. Imagine if she had gone to England for that abortion."
To loud applause, the NUI Galway arts student said: "I wouldn't be able to experience all the amazing things life has offered me."
She added: "The Eighth Amendment is so precious. It protects lives and that is priceless. A life is priceless.
"To think next year one in five babies might be aborted is unimaginable but it's the horrifying reality.
"Women need to know no matter how impossible their situation is, abortion is never the answer."
Campaign leader Niamh Ui Bhriain urged people to turn out and vote to reject abortion and the "untrustworthy political class".
She said: "The polls are turning in our favour and as the reality of the repeal slogan becomes more and more evident to voters, more and more voters are turning against this proposal.
"This is a rising of the people against the elites, and on May 25th it's time to join a rebellion, and to reject both abortion on demand and the untrustworthy political class that wants to repeal the right to life of children before birth."
Dr John Monaghan told those present that he had delivered between 4,000 and 5,000 babies during his career.
He said: "Not on one occasion was I prevented from protecting a woman's life because of the Eighth Amendment."
Dr Monaghan said Ireland is a "remarkably safe place" to be pregnant, adding: "It is a very simple observation that if the Eighth Amendment was dramatically risking the health of women, this would not be the case. The figures don't add up."
Campaign communications director John McGuirk described it as "undoubtedly a tight race" but said he is confident from feedback on the doorsteps that a No vote can prevail.
He said: "I think there's an awful lot of people, particularly outside Dublin, who tell me that the No vote is strong, it is growing and we believe we're going to win."
The No movement has a current budget of around €400,000, he said, adding that a "significant" amount of that will be spent on online campaigning.
Update: 11.52am: Pro-Life groups launch campaign with just 8 weeks to abortion referendum
With just 8 weeks to go until the abortion referendum the Pro-Life side officially launch their campaign today.
Group 'Save the 8th' say they cannot trust the Government not to change abortion laws a month after the vote.
They are criticising the Tánaiste Simon Coveney who is backing terminations up to 12 weeks - despite his earlier reservations.
Public Expenditure Minister Paschal Donohoe says it is impossible to please some people.
He said: "When we were dealing with the aftermath of the tragedy of Savita Halappanavar, I was being told because we have a party whip in place we are not recognising that some matters are matters of conscience.
"Now that the Taoiseach has recognised that there are certain matters that are matters of conscience - when people evolve or maintain their positions that is then described in a pejorative manner."
Earlier: Simon Harris advocating 'yes' vote as abortion referendum campaigning gets underway
Campaigning is due to get underway today ahead of the abortion referendum.
Yesterday, the Government announced a vote on whether the 8th Amendment should be repealed will be held on May 25.
Everyone is being encouraged to make sure they are registered to vote in order to have their say.
Health Minister Simon Harris is advocating a "yes" vote.
He said: "My message to the people of Ireland is: 'This is your chance'.
"If you can no longer accept that every year thousands of women, often in the privacy of their bedroom or their home, often without any medical supervision, are taking abortion pills - this is your chance to right that wrong."
Today sees the launch of the pro-life Save the 8th campaign.
Spokesperson Niamh Uí Bhriain says most Irish people don't support the Government's proposals for abortion legislation.
She said: "The Government isn't asking us to look at hard cases, it is asking us to legalise abortion on demand in this country and we are asking people to reject that proposal."
- Digital Desk