I asked this question with my first baby and someone said to know how it feels, simply ...

"Grap the bottom lip of your mouth and ...
pull it over the top of your head!" I did not laugh at that joke!

Other people told me it was like pooing a watermelon - that freaked me out.

But quite honestly having given birth 4 times since, its a very natural process. Simular to extra strong period pain that comes in waves of intensity. There is alot of pressure on your lower back and the lips of your vagina can feel they are stretching during the pushing stage of labour.

The greatest piece of advice I could give you is to remember that panic / fear based emotions only intensify the pain. (Just like being stressed :eek: and tense with period cramps). Try to trust your body and stay as calm as possible. I like to go into my own little 'zone'. (Not some trippy hippy zone - I just concentrate on my body and ride out contaction waves and rest my body in between each wave).
Practicing relaxing your mind and breathing (simular to meditation) is a great way to prepare.

All the best.