It is always good to recall that correlation is not causation, yet this phenomenon above has a rather strong and valuable correlation with the explanation that Minouche Shafik provides in her last year's book "A new social contract" ( good read, btw, intended to set up a discussion for a post-pandemic and post 2008 recession world. A work with an intention to be comparable to the Beveridge Report 1942. Obviously, it would need some further amendments in light of the present day).
Anyway, Baroness Shafik argues that the more working women, the higher ( whatever the definition means) the fertility rate is.
The set of countries with family-care oriented policies ( a conservative approach where the upbringing of a child is a personal issue occasionally compounded by the social praise of maternity) like Italy, Spain, Poland, Japan, and South Korea have lower birth rates and higher levels of aging population ( with the consecutive negative impact of demographic trends for future economic projections).
Whereas countries with a more developed public-service infrastructure for families ( nurseries, childcare) and shifted social attitudes towards female employment (Nordic countries followed by German-speaking world, UK and US next) have higher ( compared to the previous set) rates of fertility.
Properly understood in its social depth and designed in the right way, policies can nudge behavioral change.