Average amount of stretch marks on a healthy, fit young woman?

It depends on the woman and I feel also genetics. My first born gave me the worse stretch marks I have ever seen. By the time he was born it looked like my stomach had been mauled by a tiger I am not kidding and I had a very healthy pregnancy the whole time and I was very active. With this pregnancy I do not have as many stretch marks but I think it has to do with the fact his older brother did the most damage. I also use a lot of lotion on my belly this time around to keep my skin hydrated. No one can tell you the future of your baby belly when it comes to stretch marks, you are just going to have to wait and see...and use lotion. While it will not completely keep them away believe me it will help a lot with the itching that comes with being pregnant and the stretch marks.