My thoughts were similar to Bigshadow and those expressed by Markk, and Shiraishi Sensei through him.
I've been fortunate enough to never fall while carrying one of my kids. (Although, you can be sure I started them on breakfalls early.) But if you're carrying the child and falling correctly, there shouldn't be a problem.
However, I really liked the folks who chimed in and said they'd sacrifice their own bodies rather than hurt the baby. This is definitely true, something I've been close enought to feel, and something I think would happen quite naturally.
By example, if you're carrying the baby high on your shoulder to burp them and you fall so that it would be best to use that shoulder to take some of the impact, well you can expect that you'll tuck tigher and kick off a bit so that you come down with the stairs right in the middle of your back - or worse.
Don't worry. If you love the baby, you'll do whatever you can for it.