Women often died during childbirth. In medieval times some estimates put it at 30% of women died during one of their childbirths (but I can’t find rates on a per pregnancy basis and don’t know how many children they were having in average). Estimates are that up to 1-in-50 pregnancies killed the mother in antiquity.

I suspect it was exceptional if a woman bore more than 6 children, although obviously some women would have more than ten. I believe the baby boomer generation had large families due to excellent modern medical care post WW2.