A rally calling for the extension of the act was held outside Belfast City Hall
Pro-choice and anti-abortion campaigners have been holding rallies in support of, and in opposition to, an attempt to change the law on abortion.
Hundreds of campaigners attended an anti-abortion rally at Stormont.
An amendment to the Human Fertilisation and Embryology Bill would extend the 1967 Abortion Act to Northern Ireland.
The Alliance for Choice group, which wants the act extended, held smaller rallies outside Belfast City Hall and in Londonderry.
Alliance Party assembly member Anna Lo, who is pro-choice, told Inside Politics the amendment was "the last chance to liberalise the law on abortion".
The abortion amendment is due to be debated in the Commons on Wednesday.
Figures from all sides of the political spectrum attended the Stormont rally
However, reports from Westminster suggest the government may use a procedural motion to push it to the back of the queue, in the hope that MPs will run out of time before voting on it.
Ms Lo said: "I think that would be very sad for Northern Ireland, I think this is the only chance for a long, long time for Northern Ireland to have this liberal law."
The reason abortion law can be dealt with at Westminster rather than Stormont is that it is considered a matter of criminal justice.
MLA Dr Kieran Deeny, who opposes abortion, said this was another reason why justice powers should be devolved.
"If there ever was a medical reason for us to have police and justice powers devolved to Northern Ireland quickly, this is it," he said.
"And we should have that done as quickly as possible for the sake of our unborn children."
Saturday's "Rally for Life" at Stormont was backed by anti-abortion campaigners, politicians and church leaders.