I went to a seminar on pain management during labour and the doctor right out said something to the effect that "the women in this room have done two of the most dangerous things you can do - ride in a car and get pregnant." There *are* risks that just aren't often discussed.
I know two women whose doc made the wrong call during labour (should have had C-sections) and forceps were used. They both required at least one reconstructive surgery to repair their insides (bowel, bladder, I would assume sexual parts too). Also friends who have thrown up so much through the entire pregnancy, that they required hospitalization several times for dehydration. An internet friend who recently had her twins via C-section, almost 2 months early, because blood tests indicated that her liver was starting to malfunction more and more (part of pre-eclampsia - high blood pressure during pregnancy). Of course most people don't hit these extremes but the fact that I know all of these people indicates that it does happen.
Also, there are changes to the body ... one mom I know was on bed rest for half her pregnancy and her nice, round rear end disappeared - it went flat and wide - looks like she needs a belt to keep her pants up. Now, she had trouble getting pg and would trade her derriere any day for her babies, but still - that would bother me. I suppose she can build up again with the right exercise, though. Nevertheless it is possible to work out and have a great bod even after pgcy (for most people, as far as I know)so I don't think it's an excuse to let yourself get unhealthy.
For myself, I really enjoyed almost everything about pregnancy. I didn't get sick, had some pain but not much, etc. The worst thing was probably restrictions on food, because I do love wonderful food (especially red wine, sushi, soft cheese and runny eggs). While labour wasn't particularly fun, it wasn't horrible for me. In fact I felt strong, powerful and amazed at the whole thing. And we've also been really lucky on the sex front ... sex is even better now than before I got preg. Now this might have happened even w/o having kids, as a relationship matures and the partners grow with it ... but I think a bit of stretching actually helped us, since I am petite and my guy is much taller. Frequency is less for sure, but quality is better than ever

I consider myself lucky because I really didn't know how risky the whole deal was.
Sure, preg & delivery is "natural" and all ... but so is a high rate of mortality for women during pregnancy and delivery. (didn't one of the Bronte women die during pregnancy, because she dehydrated?) There is a perception that it's not so dangerous, yet it IS. Why do you think men went through 3 wives back in the olden days - death during childbirth and too much childbearing were big reasons. If you don't really want to have a child/get pg in the first place, why on EARTH would you expose yourself to these risks - let alone all that comes after in actually being a parent?
Andie
Ps. Do NOT read this Ps. if you are squeamish! This will totally gross you out.
I am a science/biology type person - another reason why pgcy was fascinating to me, I'm sure. Anyway after delivery I asked for the placenta so I could take it home, and put it in the freezer until I had the chance to dissect it. It was so cool! As it turns out, the placenta had an abnormality in it (which did not adversely affect us) which could have caused a big risk, however things worked out so that it didn't. And they did not spot this on ultrasound. So even with technology you can't be sure.