The new medium, called EscaSite, launched at four of the UK's largest shopping centres earlier this month.
The medium was created by Escalator Advertising, which patented the system and picked the charity because its current campaign links with the medium's use of steps.
The campaign highlights that one in five premature babies will never take their first steps and asks passers-by to contact Tommy's to help improve those babies' chances.
Jane Brewin, Tommy's chief executive, said: "We believe this medium will be instrumental in allowing our message to reach more people, in a powerful and impactful way." She said the medium was an ideal way to attract the attention of its target audience of mothers and grandparents.
Brewin said that the ads would run alongside its existing 'gingerbread man' campaign, which has been shown on TV, cinema and posters for the past 18 months.
The ad will feature in Capital Shopping Centres: the Glades in Bromley, Kent; the Harlequin in Watford; the Metro Centre in Gateshead; and Lakeside in Thurrock, with 15 further sites to come.