Both things. I had three miscarriages before I had my kids. I had an easy thing to fix: my progresterone was too low. Anyway, I wouldn't have had kids in previous generations.
Now, on to preemie births. After my 1st child, I had twins. Mine came the natural way and are a gift from God. They are identical.
Anyway, I have friends who start taking fertility drugs and never think about the consequences of taking those drugs. They increase the risk for having multiples, and it is very dangerous to have multiples.
I was on complete bedrest for over 2 months so that I would have my twins early. My twins were considered full-term and were born at 36 1/2 weeks. At 6 weeks old, they still got a serious respiratory illness (RSV) and they almost died. One has brain damage because of complications during her illness. Of course, my daughters would not be alive if it weren't for medical advancements.