Emergency services descended on Croydon Road near Penge on Sunday evening but the woman had died, police confirmed.
According to officers, the child survived although is in a serious condition.
Footage of the road on Sunday evening showed paramedics holding up a blue sheet to cover the body after they were called at 8.08pm.
More than a dozen emergency service vehicles descended on the road which remains closed.
A mother was killed while crossing the road in Anerley near Penge (Pic: Daily Star)
The mother was hit by a car in Croydon Road, Anerley. Paramedics were seen covering the body (Pic: Google)
A spokesman for the Metropolitan Police said: ‘A car was found to have been involved in a collision with a mother and a baby in a pram.
‘Despite the efforts of officers and paramedics, the mother, believed to be in her 20s, was declared dead at the scene
‘The baby has been taken to hospital. His injuries have been assessed as life-threatening.
‘Road closures have been put in place. The driver of the car, who stopped at the scene, has been taken to hospital. His injuries are non life-threatening.’
The driver has not been arrested.
Bromley Police have asked people to avoid the area.
The mother was struck by a car in Anerley (Pic: Google)
A mother was killed as she crossed the road. Police can be seen setting up a cordon (Pic: Facebook)
The blue tent was kept up after the woman was killed in the road (Pic: Facebook)