A woman who was around eight months pregnant has been stabbed to death and her baby is critically ill in hospital.
The Metropolitan Police has launched a murder probe in south London following what a senior detective described as a “horrific incident”.
The force said officers were called to reports of a woman in cardiac arrest at an address in Raymead Avenue, Thornton Heath, Croydon, at around 3.30am on Saturday.
On arrival, a 26-year-old pregnant woman was found with stab injuries.
She died at the scene, where her baby was also delivered.
The newborn remains in hospital in a critical condition, Scotland Yard said.
A 37-year-old man has been arrested on suspicion of murder and is in police custody, with the force stating officers “retain an open mind to any motive”.
Detective Chief Inspector Mick Norman said: “This is a horrific incident in which a young mother has lost her life and her child is critically ill.
“Our sympathies go out to her devastated family. They are being supported by specially trained officers following this awful event, and I would ask that they are left alone at this time as they come to terms with the enormity of what has happened.
“A large crime scene is in place, and is likely to be in place for some time.
“At the forefront of our inquiries is understanding what exactly has led to these tragic circumstances, and we are doing everything we can to establish the facts.”
Medics fought to save the mother after an air ambulance, two ambulance crews and two response cars were sent to the scene by the London Ambulance Service.
The force said the woman’s next of kin have been informed but formal identification is yet to take place. A post-mortem examination will be held in due course.
A London Ambulance Service spokesman said they were called at 3.26am on Saturday to reports of an incident on Raymead Avenue, Thornton Heath.
“We sent an incident response officer, two ambulance crews, two medics in response cars and an advanced paramedic to the scene. We also dispatched London’s Air Ambulance,” he said.
“We took one person to hospital as a priority. Sadly, despite the extensive efforts of medics, another person died at the scene.”
Reacting to the murder on Twitter, London mayor Sadiq Khan said: “Violence against women is endemic in society and devastating murders in the home, like this one, show the scale of the problem we face.
“My prayers are with this innocent child, and with the mother it has so tragically lost.”
Neighbours said that three woman, one of whom was pregnant, lived at the house and they had a small dog.
One neighbour said she had got up at about 3.30am to do her prayers when she heard a dog barking at the house, which is two doors down.
The neighbour, who did not wish to be named, said she was “shocked and surprised” to hear about the attack.
A police cordon was in place around the two-storey semi-detached house on Saturday night, with three uniformed officers stationed outside.
Lights could be seen inside the property, which is in a quiet one-way street off London Road near Croydon University Hospital.
Anyone with information should contact police on the dedicated incident room number of 0208 721 4005, or ring 101 quoting CAD 1358/June 29. Alternatively, contact Crimestoppers on 0800 555 111.