Campaign groups and union leaders have called on the British Prime Minister to give a "categoric assurance" that women's rights and access to abortion will not be used in any trade-off with the DUP.
A letter to Theresa May urges her not to "turn the clock back", or to turn her back on the women of the North.
Signatories to the letter include the Fawcett Society, TUC, Royal College of Midwives and British Pregnancy Advisory Service.
The letter says: "We are writing to seek a categorical assurance from you that you will not allow women's rights and, in particular, women's access to abortion to be used in any kind of trade-off with the Democratic Unionist Party.
"We would strongly oppose any proposal to re-open the issue of time-limits or to in any way restrict women's access to abortion.
"As you will know, unlike elsewhere in the UK, abortion is only permitted in Northern Ireland if a woman's life is at risk or there is a permanent or serious risk to her mental or physical health.
"As a result, women in Northern Ireland are forced to travel to another part of the UK in order to access the same abortion services as women in the rest of the UK.
"This affects hundreds of women each year. Only those who can afford to travel and pay for treatment - as, despite being UK taxpayers, women resident in Northern Ireland are currently not entitled to NHS funded abortion care in England - can do so."
The letter adds that the UK is a pro-choice country which supports a woman's right to choose.