Delegates voted 73 to 65, narrowly in favour of a motion calling for USI officers to lobby the Government and other relevant bodies to develop greater access to abortion services for all women in the State.
Kelly Mackey, welfare officer at the Institute of Art, Design and Technology in Dun Laoghaire, said a crucial voice which remained absent from the debate was that of the 6,000-plus Irish women who travel to Britain yearly for abortions.
"They are silenced through stigma, fear and shame. But a ban on abortion in Ireland does not mean it's not an Irish problem and having the right to travel for an abortion is a poor response to this very real issue," said Ms Mackey, who was later elected USI welfare officer.
Ms Mackey said her motion respected differing student opinions on abortion but recognised the lack of medical follow-up for those Irish women who undergo the procedure abroad.
The decision maintains a policy last adopted by USI congress five years ago.
USI president Tony McDonnell opposed the motion on the grounds that the Government and the main opposition parties are not likely to hold a referendum on the issue in the coming years.
"Why should we be seen to carry the flag for abortion when it's not going to happen; it's not something we're going to succeed on. When we campaign on it, we drive away as many people as we bring in to USI," he said.
The issue has proved divisive in the student movement in the past and many believe it's not one USI should take a stance on.
"People are giving their opinions about whether abortion is good or bad but the issue is whether USI is the body which should campaign for it and I don't think it is," said NUI Galway delegate Liam Hennelly.
But fellow NUI Galway representative Rachel O'Toole said children born to families who cannot support them are victims.
"A lot of parents don't have the means by which to go abroad and have an abortion. I have been in schools where kids have no support at all at home," she said.
Katie Morrisroe from University College Cork said she was pro-choice but opposed the motion, suggesting delegates find out the views in their own colleges and return to the motion next year.
Conversely, Trinity College Dublin delegate John McGuirk said he is very pro-life but favoured USI lobbying for abortion.
"We have a responsibility to represent the interests of our most vulnerable members to have access to these services as close to home as possible," he said.