The woman, who cannot be named for legal reasons, together with her partner, entered the house where the child was living as part of a care order and took her away in the middle of the night.
Andrew Scott, prosecuting, said the couple drove to Stranraer and took a ferry to Northern Ireland, then travelled to the Republic of Ireland with the five month old girl.
The woman subsequently turned herself in at a Gardai Station in the Republic and handed over the child to the authorities.
The 23-year-old woman admitted a charge of taking a child aged under 16 out of the United Kingdom between April 18 and 21 last year. She was jailed for 12 months.
Judge Simon Hirst, passing sentence, told the woman that under the terms of an interim care order the child was not to be removed from the United Kingdom without permission from the court.
“You knew perfectly well that you should not be taking this child [from where she was living] let alone out of the country.”
He said the child had been “significantly damaged” by the experience.
The judge added: “It seems to me impossible to suspend the inevitable custodial sentence.”
Marie Spenwyn, in mitigation, said that the defendant acted out of panic as she feared she would not see the child again: “She did not think about the consequences.”
Miss Spenwyn said the woman had a complicated history of mental health problems and in the days before her sentencing hearing had been at a psychiatric unit.