Mary Doogan and Connie Wood, who are conscientious objectors to the process, won a challenge before three appeal judges at the Court of Session in Edinburgh in April.
Their victory followed a ruling against them last year in their action against NHS Greater Glasgow and Clyde.
In the latest round of the battle, Supreme Court justices in London are to hear an appeal by the health authority at a date to be fixed.
As conscientious objectors, the women have had no direct role in pregnancy terminations.
But the midwifery sisters, who are both in their 50s, claim they should also be entitled to refuse to delegate, supervise and support staff involved in the procedures or providing care to patients during the process.
The health board argued that the right of conscientious objection was a right only to refuse to take part in activities that directly brought about the termination of a pregnancy.
In the appeal ruling in favour of the women, Lady Dorrian, with Lords Mackay and McEwan, said: “In our view the right of conscientious objection extends not only to the actual medical or surgical termination but to the whole process of treatment given for that purpose.”
After the decision Ms Doogan and Ms Wood voiced their delight and said the ruling affirmed the rights of all midwives to withdraw from a practice that would ‘’violate their conscience’’.
The women were employed as labour ward co-ordinators at the Southern General Hospital in Glasgow. At the time of the original ruling, Ms Doogan had been absent from work due to ill health since March 2010 and Ms Wood had been transferred to other work.
Both registered their conscientious objection to participation in pregnancy terminations years ago, under the Abortion Act, but became concerned when all medical terminations were moved to the labour ward in 2007.
They said being called up to supervise and support staff providing care to women having an abortion would amount to ‘’participation in treatment’’ and would breach their rights under the European Convention on Human Rights.
In the original ruling against them, the judge, Lady Smith, found that the women were sufficiently removed from involvement in pregnancy terminations to afford them appropriate respect for their beliefs.
At the Supreme Court the appeal will concern the scope of the right to conscientious objection under the Abortion Act 1967 and in particular the decision of the appeal judges that the women’s entitlement to conscientious objection includes the entitlement to refuse to supervise staff in the provision of care to patients undergoing termination.