The advert also uses the similarity altercast, as these are just ordinary women doing their job of being a mother, so people watching the advert will be able to relate to this. Brock (1965) found paint salesmen to be more influential when they had performed a job similar to the one the target faced, compared to when the salesmen was highly experienced but had had an unrelated previous job.
Brock, T. C. (1965). Communicator-recipient similarity and decision change. Journal of Personality and Social Psychology, 1, 650-654.
Regan, D. T. (1971). Effects of favor on liking and compliance. Journal of Experimental Social Psychology, 7, 627-639.