What gauge for trap shooting?

[gordread]

I'm interested in acquisition of a shotgun strictly for the purpose of skeet/trap/clay shooting.

Is a 12 gauge required? What about 20? or 410?

One of the reasons I'm asking is my wife is also interested in shooting, but she is a small lady (4'11") with a short 'wingspan' so she needs a relatively small gun with a soft recoil.

I know there are lots of makes/models/manufacturers, but I think if I can narrow it down to a particular gauge, then maybe I can find a gun that will fit.

Thanks guys.

Gordon