Stretch marks

I'm currently 28 weeks pregnant with my 3rd child. The last couple weeks I have noticed stretch marks just under and around my belly button. Could this mean I am going to have a baby that weighs more?

Here's why I ask.. with my first pregnancy i went from 100lbs to 168lbs with no stretch marks on my belly. I have them on my thighs, butt etc.

With my second pregnant I went from 115-145 with no new stretch marks especially none on my belly. I have some stretch marks on my hips but not the belly until this pregnancy.

I haven't gained any crazy amounts of weight this pregnancy or notices anything different.

So why is it that I got stretch marks now with my 3rd pregnancy...?