It is the first challenge to Ireland's abortion laws in years
The Irish Republic's strict abortion law is being challenged in the European Court of Human Rights in Strasbourg.
The legal action has been brought by three Irish women who say the effective ban on abortion in Ireland violates the European Convention on Human Rights.
All three have travelled to Britain to have abortions.
The Irish government has engaged two leading lawyers to argue its case that the country has a sovereign right to protect the life of the unborn.
The three Irish women will be identified only as A, B, and C during the Strasbourg court hearings.
They argue that being forced to travel abroad for abortions endangered their "health and well-being" as safeguarded by the European Convention on Human Rights.
The two constitutional lawyers representing the government of Ireland argue that the convention's safeguards cannot be interpreted as endorsing the right to abortion.
Abortion is illegal in Ireland, a deeply Catholic country, unless the life of the woman is in danger.
The Irish constitution was amended in 1983 to include the "Pro-Life Amendment", which asserted that the unborn child had an explicit right to life from conception.
The case is the first challenge to Ireland's abortion laws in more than 15 years, the BBC's Europe correspondent Jonny Dymond says.
Almost 140,000 Irish women have travelled to Britain over the past 30 years to have abortions, our correspondent adds.
The Irish Family Planning Association welcomed the challenge to the laws, which it described as "draconian".
It said they violated international human rights norms "because they inflict such grievous harm to women's health and well-being".
But Johanna Higgins, co-founder of the Association of Catholic Lawyers of Ireland, told the BBC's World Today programme that a ruling against Ireland would be an infringement of its ability to decide its own laws.
"Whatever the human rights aspects are of this, abortion is illegal in Ireland because it is a criminal offence," she said.
"If I were in any country and this were to go against Ireland, I would be very concerned that the Europeans feel they can step into domestic law."