So much has to do with the size of your pelvis as well - and that's not just the width of your hips, it's the size of your pelvic outlet. The shape of the inner bones of your pelvis can have an enormous influence on the birth of your baby. The midwife at our first birth was the shortest, slimmest person I ever met, and she gave birth to some large babies! She told us once she had a back injury, and when they were doing x-rays, they discovered she didn't have a coccyx (tailbone) making her pelvic outlet much larger.

The body works in mysterious ways, but overall, it does work.