Aspirin to help prevent complications

I had a 2nd term miscarriage in November that was completely unexplained. I had numerous tests done and everything came back fine, there's literally no explanation.

I'm currently 10 weeks with my rainbow and went in for my 2nd appointment today. My 1st appointment they ran even more tests and they all came back fine, so today my doctor told me to start taking 80 mg of aspirin everyday with my prenatal to help prevent complications.

Has anyone else been told this?? I'm of course going to trust my doctor and do it but I thought it was odd.

(I don't have clots, and my clot test came back neg.)