There seems to be an interesting J shaped graph with the interaction between how good a society is for women on the X axis and how many children they have on the Y axis.
At the far left hand side we have the countries where women have no education, no access to contraception, no safety or role in society without a man to protect them, no pensions when they get old, endemic levels of rape, and where their children often die in childhood. Those women have a lot of children. The worst case example is of course Afghanistan.
In the middle, women have physical safety, access to contraception, education and jobs, but no real equality. They are expected to work full time while also doing 90% of the housework and 100% of the childrearing. They are judged if they are SAHP and judged if they get someone else to look after their children while they work. They are expected to be slim and perfectly groomed throughout their lives, and failure to achieve this is seen as a moral failing. These women are able to opt out of childrearing - possibly at the cost of minor social stigma - and they do. The classic example is South Korea, where current fertility rates would reduce the population by 80% in two generations.
As you move towards the far right, where women have all the essentials and also a more equal distribution of domestic labour and childrearing- and greater state support for the latter - then the birth rate increases again, but not yet as far as the replacement rate. Is that because there isn't a perfect society is this world, or is it because even in a perfectly equal society women on average wouldn't want as many as two children? That's a theoretical question.
The priority for the world should be to get safety, education and healthcare to the women on the left hand side, and the priority for the governments of the countries at the bottom of the dip should be to work out why motherhood seems such a bad bet in their country and fix it.