The 27-year-old woman was admitted to a Dublin hospital yesterday suffering from acute abdominal pain and later collapsed, the court was told.
She had a ruptured ectopic pregnancy and had lost a significant amount of blood, which was replaced with recycled blood from the woman using a system known as "cell salvage".
The court was told she is now sedated and unable to express her wishes and will continue in that state until a certain procedure is carried out to prevent serious infection, but which could involve further bleeding and the need for a transfusion.
That must be done tomorrow morning, the court heard.
A dispute had arisen between her husband and the hospital over her wishes, the court was told.
Eileen Barrington SC, for the hospital, said the woman had told doctors, when first admitted to hospital, that she was refusing a transfusion of whole blood or red blood cells but would accept platelets or plasma.
Her emotional husband told the court yesterday his wife had signed a document used by Jehovah's Witnesses, known as the Advanced Care Directive, declaring she would never accept platelets or plasma even if her life was in danger.
He believed, because his wife was in such terrible pain, it was really hard for her to reason but it was one of their core beliefs not to accept primary blood components of red or white blood cells or plasma and platelets, although she would accept "minor fractions" of blood.
He knew his wife of eight years well and she had filled in three Advanced Care Directives over a number of years stating this, the most recent being August 2012, he said.
"At a time when she cannot make up her mind, that is what it [the directive] is there for."
Ms Barrington said the hospital was contending that the wishes expressed by the woman to doctors yesterday evening over-rode the wishes expressed in the directive.
The hospital wanted an order permitting it make the appropriate transfusion for the procedure referred to because, without that option, doctors had said there was a risk of death or serious lifelong disability.
As part of her treatment when first admitted to hospital, abdominal "packs" were inserted which put pressure on the blood vessels to prevent bleeding, counsel said.
Those packs must be removed within 36 hours and there was a risk of further bleeding in this procedure.
Granting an order allowing the hospital administer non-red blood transfusions, Mr Justice Roderick Murphy said it seemed to him, from evidence given to the court by treating doctors, the woman had the capacity the amend the Advanced Care Directive when she told doctors yesterday that she would accept plasma or platelets.
He granted the hospital the order sought.