The Soufan Centre, a counter-terrorism research organisation based in the US, estimates that there are at least 700 children born to foreign jihadists still in Syria.
Many of the youngsters will have witnessed appalling scenes of violence including executions and beheadings, while some of the older children may have even been coerced into take part in crimes against humanity.
A briefing paper published by Soufan has warned that Western countries must have a strategy to deal with the children should they return home.
They warned: "The physical territory of the caliphate is gone, but its core ideology has already been implanted in countless young and impressionable children.
"Countries need to craft a comprehensive strategy for dealing with those children who will return to their parents' countries of origin," the paper warned.
The large number of British children born in Isis territory could also complicate matters for the Government which has signalled that any Isis sympathisers with dual nationality will be stripped of their British citizenship.
Begum fled to Syria when she was aged 15, has married twice and had three children.
Two of those infants have since died as a result of malnutrition or disease, while her third child was born last week in the al-Hol refugee camp in northern Syria.
Her father, Ahmed Ali, who now lives in Bangladesh, has said he agrees with the British Government's decision to strip her of her UK citizenship.
He said: "I am on the side of the Government. I can't say whether it is right or wrong, but if the law of the land says that it is correct to cancel her citizenship then I agree.
"If she at least admitted she made a mistake then I would feel sorry for her and other people would feel sorry for her. But she does not accept her wrong."
Among the other British women who have given birth in Syria are Reema Iqbal, from London, who spent four years married to an Isis fighter who boasted of "slaughtering infidels like sheep".
Iqbal has spent the last year in a detention camp in north east Syria with hundreds of female jihadists but has said she wants to return to Britain with her two children.
Salma Haldane, one of the so called terror twins, who left Manchester when they were 16, married an Isis fighter and is known to have given birth to a baby boy.
The largest family to flee to Syria was the three Dawood sisters who joined Isis with their nine children aged between one and 11 in June 2015.
They left Bradford, West Yorkshire, to follow brother Ahmed Dawood, 21, but have disappeared without a trace.
