Must have been a donor egg. By 50 chance in downs syndrome and other genetic problems get to be 1 in 10 or worse. Chance of miscarriage goes to 50%.
Don’t know if she has other kids, but to have your first kid at 50 is pretty much impossible without a lot of intervention.
The article says “artificial insemination,” which would mean her own egg. However, it’s not like it’s a scientific website, so ...