Reasons for miscarriage

Did any of you identify why you may have had your miscarriages? I’m sure many of you are in the same boat as me, in that you have no history of health problems, no family history of fertility issues, etc. I’ve always been a healthy person (thankfully). Now I’m in the middle of my second miscarriage in 6 months, with the d&c scheduled for tomorrow. The first I was 5 weeks along and miscarried naturally and this time it’s a missed miscarriage, where I’m supposed to be 12 weeks today but the baby stopped growing at 8.5. I feel so confused and lost. I would be okay if there were an underlying issue because then I would be able to treat it. I’m 33 and never imagined it would be this hard to have a baby.