A 25-year-old man has been arrested on suspicion of the murder of heavily pregnant Kelly Mary Fauvrelle whose baby son Riley also later died, Scotland Yard said.
Fauvrelle was found by her sister with stab wounds in the early hours of June 30.
Her son was delivered but died four days later.
Police had previously said they feared a stranger had murdered postal worker Fauvrelle after creeping through a window left open in the hot weather.
They had issued CCTV footage of a potential prime suspect — a tall, slim, hooded man in light clothing and wearing gloves.
The possible prowler was swiftly walking towards Kelly’s home in Thornton Heath, South London, at 3.15am — around the time she was murdered.
He was captured by the same camera just over ten minutes later, running in the opposite direction on the other side of the road.
Detective Chief Inspector Mick Norman, leading the murder hunt, said previously that Kelly was stabbed to death in a “vicious and prolonged attack” in her ground-floor bedroom at the rear of the house.
He said Kelly’s mother, brothers and sister were all in the house when she was attacked.
They heard her screams, but the killer escaped without being seen.
Commenting on the search for the killer, Norman said: “We’ve released footage as the next step in what has been a fast-paced, and extremely challenging investigation.
“We need to identify the man shown in the images urgently, even if only to eliminate him from our inquiries.”
After the murder, police separately arrested two men, aged 37 and 29, who were both known to Fauvrelle.
Both were released on bail without charge until next month.
It left detectives confronting the possibility that a stranger could have targeted Kelly.
DCI Norman said at the time: “I am aware there is some speculation about whether Kelly’s attacker was known to her.
“At this stage we simply are not in a position to say and must retain an open mind.”
Since her death, it has emerged Fauvrelle had earlier survived a cancer scare and stunned doctors by becoming pregnant.
Favurelle worked at the Croydon postal sorting office and was a member of the Communication Workers Union.
Croydon & Sutton Amal Branch secretary Angela Whitter said: “She was over the moon when she became pregnant.”
She added: “People were always complimenting her on her growing bump and she was so looking forward to her baby’s arrival.”
ANYONE with information should call the incident room on 020 8721 4005, or Crimestoppers anonymously on 0800 555 111.
More to follow…