This happens, but it's not representative. Interesting belief, it seems like it should be self-extinguishing, the cultures that don't believe this kind of thing will tend to take over over time.
Most of the world is below replacement rate (~2.1 TFR), the rest will get there in a decade or two. Educated, empowered women delay having children, have less children, or no children. Holds across both developed and developing countries.
https://www.pewresearch.org/short-reads/2025/08/15/5-facts-a...
https://www.sas.upenn.edu/~jesusfv/Slides_London.pdf
https://www.visualcapitalist.com/cp/mapped-countries-by-fert...
Most women have watched someone go through a difficult pregnancy in their lives before they hit 20. It's not a "belief" for the people who live through it.
People used to die – frequently – from this "belief." And women still do.