Dead/Old Placenta

I went in for my monthly ultrasound today & my doctor said I have older looking placenta, kind of like it's dead in a few places. She asked if I smoked because that's usually what can cause it but I informed her that I don't & don't have literally anyone in my family who even does. She said it could be caused by other things but smoking is the top reason. Has anyone else ever had this? She's sending in my ultrasound images from today to a specialist to be looked at & said he would call me this week to set up an appointment for a more in depth ultrasound... 😕