I did no prepping down stairs at all and only had a graze despite pushing for an hour prior to a vacuum delivery as DD was posterior and completely stuck. Yup, just one little graze

I think some of it is in our genes, how stretchy our skin is, and the rest I believe is positioning (during birth) and the speed of the labour. I'm a bit skeptical that massaging the area helps.

Just my opinion though and thought I'd share