Analogy in pregnancy workout bok:

"Your pelvis is like a bag of groceries. If the bottom of the bag (the pelvic floor) is weak, your groceries (bowel, bladder, and uterus) will fall out.

Picture: thedailygreen.com

Source: http://www.on-a-soapbox.com/2010/02/least-traumatic-analogy-you-could-think.html