The video, using Nursery Rhymes Inc characters and a special song, shows parents how to carry out CPR if their child stops breathing. It is part of a new national campaign promoted with the hashtag #babyCPR.
It follows a poll of 2,000 people which said finding their baby unconscious is their biggest fear - but only one in four know what to do.
The video urges parents to call 999 immediately - unless they are alone, when they should first do one minute of CPR before calling help.
They must cover the baby's nose and mouth with their lips and give five puffs, each a second long.
Then use two fingers in the centre of the chest to give 30 pumps, at around 100 to 120 per minute.
Incy Wincy Spider, Humpty Dumpty, Jack & Jill, and the Cat & the Fiddle - voiced by comedians Adam Buxton and Tim Key.- are charcacters helping to get the message across.
VIDEO: Press the play button to watch the video.on YouTube.
St John Ambulance want people to watch and share the video, to remember the song in case things go wrong,
A spokesperson said: "Parents told us that their baby not breathing is the first aid emergency they fear the most. We know that parents find the thought of giving their baby CPR frightening so we’ve removed the fear factor and made it as easy as possible to learn.
"We’ve created a short video featuring the stars of Nursery Rhymes Inc. that shows how to give baby CPR in a reassuring unforgettable way. We want parents, grandparents and anyone who cares for infants to remember the song in case things go wrong.
"Please share it far and wide, so that as many people as possible know some first aid.
More first aid resources for parents:at http://www.sja.org.uk/Nurse...
See more first aid advice from St John Ambulance YouTube channel at https://www.youtube.com/stj...
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Visit http://www.sja.org.uk for more first aid advice and information on baby first aid training courses.