Meriam Ibrahim has now been freed on bail after being arrested by authorities at Khartoum airport on Tuesday.
She was trying to leave the country with her husband and two children after her death sentence for apostasy was overturned.
The 27 year-old was trying to use South Sudanese documents which Sudan say are not legal and were forged.
In May she was found guilty of abandoning the Islamic faith and sentenced to death and 100 lashes.
Mrs Ibrahim was brought up as an Orthodox Christian by her mother because her Muslim father wasn't involved in her life.
But under Sudanese law she was considered to have the same religion as her dad and was accused of converting, which is illegal.
After widespread international condemnation of the sentence she was released on 23 June by an appeal court but stopped the next day as she attempted to fly to the United States.
She's not allowed to leave Sudan and must attend police stations whenever she is asked to whilst she is on bail.
Andrew Boyd from Christian anti-persecution charity Release international told Premier's News Hour the situation is unclear.
Mrs Ibrahim's lawyer Sherief Ali Sherief said: "The prosecution continues to charge her.
"She's now been released from police custody and is now inside the US embassy where it is safe while we proceed to try and defend her from the charges that have no legal basis.
"We hope that our arguments to the prosecutor are accepted."