One of the three school girls from East London who traveled to Syria to join the so-called Islamic State fled the group's so-called "caliphate" and reached a refugee camp.
Shamima Begum, now 19 and very pregnant, used her sister's passport to leave the UK four years ago.
Ms. Begum left with her two closest friends during the mid-term break in February 2015.
A year later, ITV News revealed that one of the other girls, Kadiza Sultana, had been killed in an air raid on the terrorist group Raqqa Fortress.
In an interview with Anthony Lloyd, a reporter for The Times newspaper, Ms. Begum said, "I could not bear the pain and hardships of staying on the battlefield.
"But I was also worried that the child I was about to give birth would die like my other children if I stayed.
"Then I fled the caliphate.
"Now all I want is to go back to Britain."
On Wednesday, Ms. Begum's older sister, Renu, told ITV News: "I am so relieved that my sister was found safe and sound.
"We are aware that she has tried to go out.
"We lost contact with her as long as possible.
"We are happy to know that she is fine."
Begum had fled Baghuz town in eastern Syria in the fighting in recent days, but told the Times that her companions were not doing the same.
She said, "I respect their decision.
"They called for patience and endurance in the caliphate and chose to stay in Baghuz.
"They would be ashamed of me if they survived the bombing and were fighting to learn that I was gone."
She added: "They made their choice as single women because their husband was already dead.
"It was their own choice as women to stay."
Addressing ITV News, Ms. Begum's sister, Renu, pleaded for the UK government to allow her to return to the UK.
"She's pregnant and vulnerable, and it's important that we take her out of the al-Hawl camp and home as soon as possible."
"We hope the UK government will help bring her home where she belongs.
"This news shocked us and I ask the media to leave us a little space."