A spokeswoman for London Ambulance Service said: "We were called just before 12.40 today to reports of an incident in Eltham High Street, and sent one crew.
"Our staff treated a baby boy who had been taken unwell, who was taken to Queen Elizabeth Hospital, Woolwich."
More top news
The London Marathon brings together thousands of people raising money for charity - not to mention some rather unusual costumes.
Planning on going to the London Marathon tomorrow? Read our handy guide first!
Celebrations to mark St George's Day have started in Trafalgar Square with feasts and tea to be found in abundance.