I've done my family tree quite far back and there are no child/maternal deaths except one from whooping cough and one who fell off a swing.
All the women tended to have 5 DCs quite spread out.
This makes sense in the pre formula days when babies were breastfed for 4 years which acted as a contraceptive and spread out births.
Families of 10 only came about after bottle feeding and early weaning were brought in.
In the past most first time mums (almost always the hardest birth) were still teenagers whose bodies are better equipped for childbirth. I think the ideal biological age is 19. I also read that as people were less mobile before cars and trains they 'mated' with men from their local area who would have tended to be from the same 'stock'. Ie there was less hip/height incompatibility. Eg Short women married short men and had short babies.
Also before the medical profession invaded childbirth babies were delivered by midwives 'wise women' who were highly skilled in dealing with problem births.
TRIGGER WARNING
The aim was for the woman to survive. The baby was a bonus. I've seen the instruments they used to remove foetuses during difficult births if the mother was at risk. This is very different from now where it's the woman who is butchered because a perfect baby is the desired outcome.
Also with these midwife led home births there was no cross contamination of disease between patients so the infection rate was low. When women started going to hospital to deliver and doctors didn't know about cross contamination of bacteria they used to go between patients without washing their hands. They were literally killing their patients. Post parting infection was the number one cause of maternal mortality.
I also think that because we don't see childbirth growing up, like they used to it is shrouded in mystery until we have our own. This fear of the unknown makes women anxious at a time when relaxation will make the natural process easier.
So many modern customs of birth are setting women up to fail which is causing so much more maternal morbidity than need be. Eg inductions routinely carried out at 40+10. It is normal and healthy for pregnancy to last 37-42 weeks. Women aren't allowed to move about or eat or drink during labour (not everywhere).
Another cause I've read of difficult positioning of the foetus is modern chairs which encourage slouching. I read that we'd have easier births if we spent the last weeks on all fours like our ancestors did.