A pregnant woman lost her baby following an attack on the street in London in which she was repeatedly kicked in the stomach.
The 21-year-old, who was 32 weeks pregnant, was attacked by two men wearing motorcycle helmets in Peckham, southeast London, on Monday night.
She has been named in media reports as Bedfordshire University graduate Malorie Bantala.
Scotland Yard said there was a "strong likelihood" the men were trying to kill the unborn child and the attack is being treated as "akin to murder".
A 20-year-old man from south London, who was arrested on suspicion of child destruction and grievous bodily harm, is being questioned by police.
It has emerged that police had to bring the woman to hospital after waiting for more than an hour for an ambulance that never arrived.
The London Ambulance Service has apologised and said it is looking into what happened.
A spokeswoman said: "We were called at 8.16pm on 15 June to Talfourd Place, SE15.
"We are very sorry that we were unable to send an ambulance before we were cancelled by the police at 9.25pm and are now looking into the circumstances of what happened."
She confirmed that the LAS did not attend and that police officers took the woman to a south London Hospital.
Meanwhile, Detective Chief Inspector Robert Pack from the Homicide and Major Crime Command described the attack as "truly abhorrent and vile."
He said: "The men who attacked her must have known the impact their actions would have when they kicked her repeatedly in the stomach.
"It is sickening to think someone would deliberately target a pregnant woman in this way."
Scotland Yard said the assault happened as the woman walked home along Talfourd Place in Peckham around 8pm.
She was approached by two men who pushed her to the ground and continually kicked and stamped on her stomach.
The suspects - who are described as black and in their 20s - then ran off.
DCI Pack said the woman remains in a critical condition in intensive care, but she has managed to provide an account of the attack to officers.
"From what we know at the moment, the working hypothesis is that it was targeted at that unborn child," he said.
"There doesn't appear to be any blows or physical force directed to her head or face. It seems to be all the violence was targeted towards the child."
