I suppose that the jpouch gets pushed down and back...sort of flattened (this is speculation, not knowledge)...it is the bladder that sits directly under the baby (explains why you need to pee every hour!).
For k pouchers, it is more difficult because of the position of the pouch on the abdominal wall. I was warned (in 1979) not to get pregnant because the pouch couldn't handle it...now we know that with some help (keeping the catheter in the pouch for the last months) that it is doable.
Where there is a will, there is a way.
Good luck to all who are trying and congratulations to those who have succeeded!
Sharon