With that many kids the older ones are probably helping raise the younger. My wife's cousin has 5 kids (in relatively short intervals, I think there's less than 10 years between the oldest and youngest) & the 2 oldest ones help out a lot.
Even if we're being that cynical - taking on much more work than you can handle and increasing your expenses multiple multiple times for the next 20 years - that's not retirement.
Sweden also pays you per kid. At 11 kids you'd get about $24k a year since it scales up. As long as you live in a cheap area you don't have to spend that much money on the kids, since you don't pay for education or healthcare or daycare. Also since you are on parental leave you still get that money.
Countries like Sweden have many forms of welfare. A lot of people are working for cultural and pride reasons and not because they would be living under a bridge or on Howard St if they weren't working.
But it doesn't matter. I don't care if someone decides they want 12 kids, even if it is to avoid work. As long as those 12 kids are taken care of - and it isn't causing the women health issues at all - I'm not concerned, though I hope that at least some of those 12 are adoptions or foster children.
Some people really like to raise children, multiples.
But lets not forget that children are work. More children, more work. The thought that you are 'retiring' and relaxing just isn't so: for 14+ years, you always have a diaper to change, you always need to keep a childproof house, you always need to toilet train someone. For some years, you always have a preteen to watch over. Someone just going off to college. Etc.
But again, this isn't the norm. Even large families rarely have so many children. The amount of folks that try to have 12 children is such a small portion that it isn't worth worrying about and honestly, just parrots right-wing fears that folks are having children to get money from the government.