Government air strikes in recent days have pounded rebel-held areas of Aleppo, where more than 250,000 civilians are trapped.
Britain's permanent representative to the UN said the attacks had "unleashed a new hell on Aleppo", which he described as war crimes.
In the middle of the conflict there are at least 100,000 children, aid agencies estimate.
On Sunday, Save the Children warned that approximately half the casualties being treated in eastern Aleppo were children.
It said injured children were dying on the floors of hospitals due to shortages of equipment and medicines.
"Across the board things have never been worse for Syrian children," the group's humanitarian emergencies spokesperson, Caroline Anning, told the BBC.
Rawan has reportedly lost her entire family, including four siblings, Sky News reports.
But why are children so badly affected in the battle for Aleppo?
Syria's population, like that of many other countries in the region, is relatively young, with an estimated median age of 24.1.
About half of the nearly five million refugees who have fled Syria are children. But eight million children remain in the war-torn country, according to Unicef.
In eastern Aleppo, Save the Children estimates about 40% of the besieged population are children.
While this means the recent casualty numbers it reported appear to be roughly proportionate with the population, it is out of step with what should be happening in a war zone.
In war, you should expect to see a much higher population of adult males being killed in frontline action, Ms Anning says.
"But what we have seen in Aleppo in the last couple of days is totally indiscriminate bombing from the air," she says. "So children are impacted just as much or more than adults in those situations."
These tactics, combined with a continued siege preventing anyone from leaving the area, has created one of the worst situations for Syrian children in more than five years of war.
When bombs rain down on densely populated urban areas like eastern Aleppo, there is nowhere to escape.
And children are inherently vulnerable.
"They will often be playing outside, their movements will sometimes be less predictable, they may not instinctively run from danger," Hannah Stoddard, advocacy director for the War Child charity says.
This is compounded by the fact that school and hospitals, places where children are more likely to be present, are being targeted by the Syrian government.
In terms of injuries, children are also at greater risk. Blood loss is more devastating for them and fractures occur more easily.
The images of Alan Kurdi, Omran Daqneesh and now Rawan Alowsh might have captured fleeting global attention, but they are by no means exceptional cases that happened to be captured on film.
Rescue teams are finding children every day under piles of rubble.
"What pictures don't show is the mental scars that [these] children carry with them," says Ms Stoddard of War Child, which works with Syrian refugee children in Jordan.
"In the majority of cases, these children have lost one or more family members. They may be the sole survivor."
An immediate ceasefire is a prerequisite to any solution that could bring an end to the suffering of Aleppo's children, aid groups say.
Given the breakdown of a US and Russian brokered ceasefire last week and a spike in tensions between the two powers, the prospects for this appear slim.
Still, if a ceasefire were to happen, sustained humanitarian access to all besieged areas could be possible, Ms Anning says.
Groups need to be able to freely move in "whatever aid is needed without preconditions, and evacuate medical casualties."
The haunting cries of five-year-old Rawan Alowsh, pulled alive from rubble in Aleppo by her ponytail, have reminded the world once again that behind the politics of Syria's civil war are millions of vulnerable children.