Up to four Labour TDs could break ranks and defy the party whip on the issue.
Despite Labour fighting the last general election on a pledge to legislate for the X case, the lack of a time limit for terminations under the proposed law is causing concern for a number of backbenchers.
Voting against party policy would lead to TDs being expelled from the parliamentary party.
This would prove a major headache for Mr Gilmore, as he has already seen five of his deputies either resign the whip in protest at his leadership, or thrown out for voting against Government legislation.
If four TDs oppose the legislation, that would leave nine TDs outside the whip — a quarter of the Labour total elected in 2011.
The threatened revolt explains why Mr Gilmore is so keen to avoid a formal Dáil vote on the issue.
To force a vote on the issue, 10 or more Dáil deputies must demand it when the legislation is expected before the Oireachtas in June and July.
The Coalition had hoped to avoid rebellions by pushing the Protection of Life During Pregnancy Bill through on the nod as it is backed by Sinn Féin and almost all of the Independent TDs. However, Fianna Fáil’s position has thrown this strategy into doubt.
FF leader Micheál Martin was forced to allow his TDs a free vote on the issue after finance spokesman Michael McGrath pushed for the loosening of party discipline on the matter.
Galway TD Colm Keaveney, who remains chairman of the Labour Party despite losing the whip after voting against Budget cuts to child allowance, has led calls opposing the legislation due to the lack of a time limit on when terminations can be carried out.
Anti-legislation TDs from across the Dáil have also expressed concern about the inclusion of suicidal risk as grounds for a termination.
The Government has cited the confines of the 1992 X case ruling as the reason why no time limit has been imposed on terminations in the legislation.
Mr Gilmore made it clear over the weekend that the Government would not seek a vote on the legislation as he said the Government parties are united on it.
Taoiseach Enda Kenny has firmly ruled out allowing Fine Gael TDs and senators a free vote on the matter.
An Oireachtas health committee report on hearings it held regarding the legislation called for greater consideration to be given to the issue of suicide grounds, penalties and conscientious objections by medical staff.