One-year-old Taahyra Kasham was being pushed along a London street in her pram by her mum, Rajna, when a reflector from a streetlight was dropped by a workman above and hit her on the head.
Street light operative Joseph Parker, 25, who at the time of the incident lived in Romford, Essex, was fined after the Health and Safety Executive (HSE) found he had not erected temporary barriers around the lamp while he was working.
City of London Magistrates' Court heard that Mr Parker was instructed by his employer, Volker Highways Ltd, to investigate a faulty street lamp on Gillett Square in Hackney on 20 January 2010.
However, when he detached the reflector at the top of the lamp post it fell toward the mother and daughter below. The two-year-old needed stitches to her wound, but her mum escaped unhurt.
The HSE investigation found the incident was entirely preventable. Temporary barriers should have been used to segregate pedestrians from the work area around the lamp before Mr Parker dismantled the reflector.
HSE inspector Zameer Bhunnoo said: "This was a serious incident that needlessly injured a small child and caused her mother understandable distress.
"No blame can be attached to Volker Highways as Mr Parker had been properly trained by his employer to carry out this kind of work safely.
"Individual employees must realise that they face criminal prosecution by the HSE if they show a reckless disregard for health and safety, putting others at serious risk."
Joseph Parker, who at the time of the incident lived in Boxmoor Road, Romford, Essex, pleaded guilty to breaching Section 7(a) of the Health and Safety at Work etc. Act 1974. He was fined £2,250 and ordered to pay costs of £2,888.