Syria Kurds repatriate Islamic State-linked US, German children
Abdelkarim Omar, a senior official with the Kurdish authorities in northeastern Syria, said the handover went ahead on Friday.
"An American child and three German children with their mother were handed over to their governments," he said in a statement on Twitter.
A Kurdish source said the American girl - who was born in 2016 - was handed over to a US official at the Samalka crossing with Iraqi Kurdistan, but could not provide any further details about her parents.
Germany's Bild newspaper has reported the American child was the daughter of the German woman's first husband, who was a US citizen.
The Kurdish-majority Syrian Democratic Forces (SDF) hold hundreds of foreign men and thousands of related women and children suspected of links to the Islamic State group.
The handover comes as part of a recent spate of repatriations, many of which were triggered by a Turkish decision to deport foreign IS members and suspects in Ankara's custody.
The Kurdish forces have repeatedly urged Western countries to repatriate their citizens linked to IS, but until recently, many have refused to do so.
Germany on Friday said it was repatriating its first IS suspect, and that she and her three German children had crossed into Iraq on their way home.
Spiegel magazine named the mother as Laura H, and said she and her children had been living in the overcrowded Al-Hol camp for the displaced in northeastern Syria.
She is believed to have travelled to Syria from Giessen in central Germany in March 2016, and to have joined IS that summer.
Germany had already brought home a handful of orphans, but no adults until Friday.
Austria, France and Belgium have also repatriated some orphaned children, while the United States has repatriated several women and their children. The United Kingdom announced earlier this week it would begin the repatriation of British orphans of IS fighters.
A French woman who took her three children to Syria to join the Islamic State group in 2014 was sentenced to 14 years in jail on Friday.
A Paris court convicted Jihane Makhzoumi of charges including terrorism and child abandonment.