I disagree. I would guess the cause is women gaining agency to dictate how many children they birth, from a combination of being able to control when they have sex, birth control, and access to abortion.
It just so happens that women generally do not have these things in poorer societies.
Because, in fact, life of existing children matter to poor too and new child often means that older gets less food or have to stop education.
It's not just that. There's a level of wealth where people just choose to delay having kids
Also, in poorer countries, one’s physical securities may be more strongly related to the size of one’s family.
> Estimates suggest that more than 160 million women and adolescents who wanted to avoid pregnancy were not using contraceptives in 2019, despite significant progress in the use of modern contraceptives globally over the previous 50 years.
> Major disparities in contraceptive use still exist between regions – with more than half the women with unmet need for contraception living in sub-Saharan Africa and South Asia.
Generally means that there are exceptions, with those Indian states being one of them. Good for India to have made significant progress on women’s rights.
Some women in some subcultures may choose to have more kids than others, but by and large, giving birth and raising a baby is not a walk in the park, so I cannot see many women jumping up and down to have more than 2 or 3 kids.