I don't want to get too in the weeds in this thread, but the evidence is total fertility rate is declining across all income strata, with some evidence in some places higher income women have slightly increased fertility.

https://ifstudies.org/blog/more-money-more-babies-whats-the-... ("On the whole, a clear conclusion emerges: because different cultural groups often have unique income levels, efforts to correlate income and fertility are often deeply misleading. Global fertility decline was kicked off almost entirely by normative and cultural processes, not strictly economic ones. The effect of income on fertility is not even remotely consistent across cultures or even across times. When whole societies become richer, they do not necessarily have fewer children. Once we control for the basic problem of cultural stratification, the supposed link between low income and high fertility, or high fertility and low income, largely disappears.")

https://www.demographic-research.org/articles/volume/51/26

https://www.sas.upenn.edu/~jesusfv/Slides_London.pdf