Have you tried asking them? In particular, asking the women who are making the career-or-children decision?
South Korea is invoked, but it seems like the population there has almost perfectly levelled out at just over 51m: https://www.macrotrends.net/global-metrics/countries/kor/sou... of which 20m live in Seoul.
This discussion comes up a lot on HN, and it seems to be one where there are answers, but people don't like the answers, so they go back to feigning ignorance.