I would raise the question of how those babies are to be raised.
Humans are what's known as a pretty "altricial" species as they go - meaning a species whose young need a lot of care before they can sustain themselves independently. This trait is often associated with learning potential and adult intelligence, which makes some sense if you figure that intelligence requires learning, and that learning requires a safe a protected space that allows one to make mistakes and focus on things other than immediate survival.
I think Alison Gopnik is an interesting author in terms of tying those concepts together to understand human nature - she points out how humans become "self-sufficient" in terms of producing as many calories as they consume at much more advanced ages than chimpanzees do, and that humans are the only known species that has not only the mother caring for children, but also the father, and also grandparents, and also random other community members. Apparently you have species with some of those, like many birds have both parents care for their offspring, orcas have post-menopausal grandmothers caring for offspring, other species have various members of the community caring for offspring, but only humans do all of it.
So all that to say... If you do have your technology inducing 12 babies in a pregnancy at the cost of the mother's life with pre-20th century technology, how are those babies growing to reproductive age? Or even to toddlerhood? Are we looking at a 12:1 baby to adult ratio? Say milk isn't an issue because you have enough cows - that's still 12 babies the father needs to feed, with only two hands and so many bottles and a certain incompressible human need for sleep. Is he getting help? You talk about "government" so the "government" could help but it would still need people to assign to that job. So who's helping, other fathers with 12 babies to feed? Or women who haven't had babies yet, and if so - why haven't they, if we're so desperate for babies that we're inducing 12tuplets? Say the father gets 3 other women to help for a 3:1 baby to adult ratio, couldn't you have had better results by having those three women and the dead mother of 12 have 3 babies each instead, resulting in as many babies and 1 more adult to care for them?
That's an issue with comparing our litter numbers to Arctic foxes and other mammals - we're not Arctic foxes and there might be a reason for that.
But the weirdest thing even there is that... People can have 12 babies and more, with pre-20th century technology, and have them grow to adulthood, just fine! Better than Arctic foxes or any mammal that's at equilibrium with its environment, regardless of litter size. Just combine decent nutrition & hygiene with a total lack of birth control. I saw the numbers myself looking at my family's genealogy and looking for birth records in the late 19th century in my country and going "this family had this baby, but when's the marriage record? Let's look the previous year. Ah, another baby! And the previous year. And the previous year. And previous. Ok no baby here, maybe look at the previous year's marriage record". It didn't fail, and yes you ended up with 12 babies or so. And the craziest thing is, the death records in the margins indicated all those babies lived long and fruitful lives (obviously I'm not claiming the mortality rate was zero, just saying it's weird all those I looked up lived, the survival rate had to be really high). It must have been an insane time in that country's history. Point being, humans are fertile as hell. That's another point Alison Gopnik makes actually - we have babies more frequently than chimpanzees do, which kind of suggests dark things about the infant mortality rate when we had no birth control and our population growth wasn't insanely high.
So I'm having a bit of a suspension of disbelief issue with your very premise, that there could ever be a situation where it's better for the population growth rate to have 12 babies in one pregnancy at the cost of the mother's life instead of having 12 babies one at a time over the whole span of a mother's fertility, with said mother contributing to childcare over that time period more than she could if she were dead. And also each baby being born at term, reaping the full benefits of human pregnancy (which there are also fun things to read on - look up the article "why pregnancy is a biological war between mother and baby" to see just how greedy human babies are in the womb, and why by extension it might be a huge handicap to be one of 12 fighting in there). Yes, at most times in human history families didn't have 12 children surviving to adulthood because there was a high mortality rate - but any time in human history that wasn't great for 12 sequential children would be a million times worse for 12tuplets. 12tuplets are barely sustainable now. I say "barely sustainable" - your own research says the pregnancy itself isn't doable, I'm saying on the "taking care of them after" front, which is even more important because it's harder to handwave. We don't know how bodies work, I can see someone imagining 12 babies coming out of there. But I think it's easier for most (especially anyone with experience with babies) to picture one adult with 12 screaming babies with no outside help and quickly see the impossibility of that scenario.
On the medical/pregnancy side though honestly I'm wondering a bit at how glib you are in associating "pre-20th century tech" with "so don't expect the mother to survive". Forget about the mother, if you knew anything about prematurity and pre-20th century tech you would know there was no way for the babies to survive. So why this focus on the mother's death.