A heavily pregnant woman has lost her baby after she was repeatedly kicked in the stomach in a "sickening" assault in the street.
The 21-year-old woman, who was 32 weeks pregnant, was attacked by two men wearing motorcycle helmets in Peckham, south-east London, on Monday night.
Scotland Yard said a 20-year-old man has been arrested and remains in custody, as the force appealed for witnesses to come forward.
Detective Chief Inspector Robert Pack, from the Homicide and Major Crime Command, said: "This was a truly abhorrent and vile attack on a heavily pregnant woman who has now, tragically, lost her baby."
Scotland Yard said the "brutal assault" happened as the woman walked along Talfourd Place in Peckham at around 8pm.
She was approached by two men who pushed her to the ground and continually kicked and stamped on her stomach, police said. The suspects then ran off, still wearing their helmets, in the direction of Denmark Road.
A member of the public alerted police and officers administered first aid at the scene. The victim was then rushed to a south London hospital where she lost her baby.
The woman remains in a critical condition in intensive care, Scotland Yard said.
Mr Pack 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.
"The suspects were distinctive in their crash helmets and we would appeal for anyone who saw them either before the attack or running from the scene to please come forward and contact us."
Police said the two suspects were black and aged in their 20s.
Anyone with information is asked to contact the incident room on 020 8345 3985 or Crimestoppers anonymously on 0800 555 111.