The girl, known as Miss D, is almost 18 weeks pregnant, and the fetus has a major brain defect, The Irish Times reported Wednesday.
The government's Health Services Executive, which serves as the girl's guardian, argued that Miss D could not leave the country without court permission.
The girl learned last month that the baby has a condition in which a major part of the brain is missing. The baby has a prognosis of three days survival after birth.
Abortion is illegal in Ireland, except when the mother is threatened by a medical condition or a suicide risk. The BBC said an estimated 7,000 women travel outside Ireland each year to terminate unwanted pregnancies.