Any woman with a stable well paying job will try to avoid the very real risks of getting passed over for promotions or illegally fired. A lot of employers still see a mother as someone who can't be dedicated to work or takes too much time off.
Then you have Hispanic Americans with much higher fertility than all other groups, even if you account for income. I think it points to a cultural problem where some women see having a child as too much of a risk, becoming dependent on a man and losing it all if he decides to abandon you.
In a more community minded culture you know you have a support network to fall back on if your husband leaves you behind. And if kids are too much of a burden you can leave them with a relative until you're ready to take them in again, and you can be confident they will get raised good. That makes the risks a lot less scary.
In these places where people have more children but are overall much poorer, is there a different in infant mortality rate? I know in the past, people having large numbers of children was in part a response to the fact that the infant mortality rate was higher.
There can be a whole lot of reasons for that.
poorer people are more likely to be uneducated, have less access to contraception.
Poor people have higher infant mortality.
Children also make people poorer. the higher the fertility rate the more likely that someone will be poor.
Poorer people also tend to be more religious which can limit women's rights, their options, and increase the expectations placed on them when it comes to having children. That's especially true in undeveloped countries where women may have no choice at all.
Especially true in places where women are prevented from attaining most other kinds of status and titles. There are many positive things about being a parent, but none of them can make up for not having a choice in the matter. For people who choose to have kids though, most of them don't regret that decision.
This is going to be heavily skewed by the fact that Millenial women are in their 30s and thus will be subject to various methodologies in how they're counted for this "lifetime" figure.
My experience is that women in the US over 40 vs women under 40 (as of 2026) have a much different view of children and of marriage. This would line up with cultural changes which occurred during the early 2000s.
As for cost, this idea is promoted all the time but poor people in developed countries and poor people in undeveloped countries have much higher fertility rates. Poor people have more children, therefore it cannot be an issue of cost alone.