PAH, or Paradoxical Adipose Hyperplasia, is a rare situation in which adipose tissue (in this case fatty tissue) actually increases at the treatment location, rather than decreasing as desired. According to Zeltiq (the makers of CoolSculpting), the reported incidence of this condition is ~0.02% (1 in 5000). When considering CoolSculpting you should always review all of the potential side effects before deciding whether the procedure is right for you; however, PAH is extremely rare and CoolSculpting remains one of the best options for safe and effective non-surgical body sculpting.
In our studies and usage, we've found CoolSculpting to be more effective than UltraShape, and would recommend CoolSculpting accordingly. Definitely seek a consultation in your area so that the specifics of your particular treatment regimen can be identified, and I recommend you ask to see before/after pictures done by that provider, not solely the company sponsored photos.