Shamima Begum had hoped to bring her approximately three-week-old son Jarrah to the U.K. with her.

“Ms. Hoda Muthana is not a U.S. citizen and will not be admitted into the United States,” U.S. Secretary of State Mike Pompeo said.

Shamima Begum, a teenager who left London when she was aged 15 to join Islamic State in Syria, has had her British citizenship revoked, according to a letter sent to her family published by ITV News.

Shamima Begum was one of a group of schoolgirls from London’s Bethnal Green neighborhood who went to Syria to marry IS fighters in 2015