The court found that turning her life support off did not violate the Eighth Amendment of Irish law which holds that fetus and mother have equal rights and both are considered citizens.
One judge stated the case had nothing to do with abortion.
The three-judge panel, which consisted of president of the High Court Justice Nicholas Kearns, Justice Marie Baker and Justice Caroline Costello, stated that keeping the mother on life support was a "distressing exercise in futility".
"The entire medical evidence in this case goes one way only, and that is to establish that the prospects for a successful delivery of a live baby in this case are virtually non existent" said Judge Kearns in a 29 page written ruling.
Justice Kearns said the court "is satisfied" that the medical advice calling for the life support to be terminated is correct.
In his judgment, Justice Kearns said: "To maintain and continue the present somatic support for the mother would deprive her of dignity in death and subject her father, her partner and her young children to unimaginable distress in a futile exercise which commenced only because of fears held by treating medical specialists of potential consequences."
The young mother, who has two children, collapsed and died from a brain hemorrhage but doctors in the hospital she was rushed to would not take her off life support as they were fearful of the legal consequences.
However, doctors and experts had argued unanimously that the fetus could not survive so early in the pregnancy. Advocates had also argued for the support of the family's wishes and the rights of the woman.