Are Miscarriages Genetic?

Se

I'm almost 8 weeks pregnant and so nervous that I'm going to miscarry because my mom and her sister each had several miscarriages. My mom was in her 20s and perfectly healthy but her sister was in her mid-late 30s so her age may have contributed. Also, my mom, aunt and their mom all went into labor 3 weeks early, which is part of the reason I feel like this sort of thing may be genetic.

Doctors say it usually isn't genetic (from what I've read) but what are your experiences?

Its hard to be excited when I'm so nervous about it!