The assembly is debating a motion that seeks to reject recent changes to Northern Ireland’s abortion laws.
New legislation drafted by the Northern Ireland Office took affect in March, after a vote at Westminster in 2019.
Tuesday’s debate will see the DUP and Sinn Féin oppose different aspects of the legislation.
The motion, if approved, will not change the law, but Arlene Foster said it would “send a message” that Stormont does not support the regulations.
The DUP, which is staunchly opposed to abortion, has proposed the debate. It wants the assembly to create its own legislation and overturn the laws enforced by Westminster.
Under the new regulations from 31 March, abortion is permitted in all circumstances in Northern Ireland in the first 12 weeks of pregnancy.
A limit of 24 weeks applies in situations where continuing the pregnancy would involve risk of injury to the woman’s physical or mental health.
No time limit applies in cases of fatal fetal abnormality, where there is a substantial risk that the fetus would die or, if born, would suffer a severe mental or physical impairment.
That element of the law has been interpreted by some as meaning terminations could be carried out with no time limit, in cases of Down’s syndrome, cleft palate or club foot.
Figures show that from 31 March to 22 May, 129 abortions have been carried out in Northern Ireland.
The statistics were revealed by Health Minister Robin Swann in an answer to a question from DUP assembly member Paul Givan.
Figures from 2018, show 1,053 women from Northern Ireland travelled to England and Wales for an abortion in that year.
The DUP is calling for the rejection of “the imposition of abortion legislation which extends to all non-fatal disabilities, including Down’s syndrome”.
Sinn Féin does not support the DUP’s motion.
Instead, it has proposed an amendment that would alter the motion, to state that the assembly “rejects the specific legislative provision in the abortion legislation which goes beyond fatal fetal abnormalities to include non-fatal disabilities, including Down’s syndrome”.
Sinn Féin changed its policy on abortion in 2018 to support terminations in all circumstances up to 12 weeks.
It had already backed making terminations available in circumstances like fatal fetal abnormality, rape or sexual abuse.
However, this amendment drafted by the party indicates it wants the Westminster legislation amended, when it comes to cases of non-fatal disability.
Westminster sources said the UK government remains under a legal duty to implement recommendations made in 2018 by the United Nations Committee on the Elimination of Discrimination against Women (CEDAW).
That report said abortions should be allowed in Northern Ireland where there is “severe fetal impairment”, but that provision should not “perpetuate stereotypes” towards disabled people.
Speaking on the BBC’s Inside Politics programme, Sinn Féin assembly member Philip McGuigan said his party did not support those recommendations on abortions relating to severe impairments, and stressed the need for an “all-island approach to healthcare for women”.
In the Republic of Ireland, abortions are allowed in cases of fatal fetal abnormality, but it does not extend to conditions such as Down’s syndrome.
Both Sinn Féin and the DUP have also cited Heidi Crowter, who has Down’s syndrome, and who has been campaigning for a change in England’s laws, where pregnancies can be terminated at any time up until birth, in the cases of Down’s syndrome.
Pro-choice campaign group, Alliance for Choice, criticised Sinn Féin’s proposal, arguing if it were to lead to a change in the abortion regulations, some women from Northern Ireland would have to travel to England for terminations.
How did we get here?
Last July, MPs at Westminster voted to decriminalise abortion in Northern Ireland and create new laws.
Stormont was not functioning due to a row between the main power-sharing parties.
Prior to that Commons’ vote, abortion was only allowed in very specific circumstances in Northern Ireland.
It then fell to the Northern Ireland Office to come up with a framework to oversee the provision for abortion services.
In March, the regulations were made public for the first time and set out when and where abortions could take place, as well as who could carry them out.
The following month, Northern Ireland’s Department of Health instructed health trusts that abortions could now be carried out lawfully, in line with the regulations.
However, services are being provided on an interim basis as full abortion provision has not yet been commissioned.
Health Minister Robin Swann said it was a cross-cutting matter that needed to be approved by the whole executive.