Abortion has been decriminalised in Northern Ireland, despite widespread opposition, after the laws changed at midnight.
A last ditch attempt to halt the changes saw the reconvening of the Assembly on Monday but it was not enough to stop the new laws from coming into effect.
In what is now the most liberal abortion regime in the UK, women and girls in Northern Ireland can terminate their pregnancies up to the point of viability without prosecution.
But the changes strip away many other protections that were in place, including the protection of women from coerced abortions.
New regulations governing abortion in the province will not be ready until the end of March 2020.
Pro-lifers have vowed to continue advocating for the rights of the unborn as the regulations are drawn up.
Dawn McAvoy, co-founder of pro-life group Both Lives Matter, said: "We have had over 1000 days without government, and pro-abortion activists have sadly taken advantage of that.
"Their answer to pregnancy crisis is abortion. We say women deserve better than abortion. They deserve to be supported to choose life. So we ask our politicans to not waste any more days."
"Both lives will always matter so this is not the end, only the end of the beginning and we will work through the consultation process and regulations to ensure both lives matter.
"And when the Assembly is reconvened, we will work to reverse bad law implemented through a bad process which will lead to bad consequences for women and their unborn children."
Liam Gibson, political officer at the Society for the Protection of the Unborn, said: "It is a very dark day for Northern Ireland and for all those who believe in the inviolability of human life."
Changes to the law in Northern Ireland were voted through by MPs in Westminster in the absence of a sitting Assembly despite strong opposition in the province.
A poll earlier this month by LucidTalk for Both Lives Matter found that over half of adults in Northern Ireland did not support the changes.
Nola Leach, chief executive of CARE (Christian Action Research Education), said the changes were "tragic".
"It's tragic because devolution has been ignored and by-passed by MPs and Peers at Westminster and there will be long-term consequences of them doing so," she said.
"It is doubly tragic because the new laws will endanger women and babies, rather than protecting them.
"This is not progress; it is a retrograde step. Abortion will now be legal in Northern Ireland on the grounds of disability and gender, there will be no effective regulation until at least March 2020 and even that is not guaranteed.
"The people of Northern Ireland deserve more than this. We continue to believe that both lives matter and our work to be a voice for the voiceless and to argue for a better way that upholds the dignity of both mothers and babies."