I can't say anything about Warsaw bloc countries but I can surely say about was going in early 90's after Soviet Union dissolution. Because - a) I was there, b) I researched the topic quite a lot.

1. Actually the fertility rate was falling quietly but steadily alongside the rise of urbanization.

2. In many countries such as Ukraine the production of consumer goods has fallen in the 90's yet there were no deficit (empty shops) due to even greater loss of purchasing power. Basically in Soviet times they had more cash but goods production was lacking and after that situation reversed. Shock doctrine - liberalization of markets - pushed most of the people into poverty.

From what I've read about Poland - shock doctrine also contributed negatively to socioeconomic factors (at least initially). There was a decrease in GDP in 1990 of 7 percent and the same decrease -7% in 1991. So drop in fertility wouldn't be that sudden after all.

There has been decline before 1990, but the drop in fertility between 1990 and 2000 is very pronounced.

https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?location...

Economic crash in Poland, Czechia or Hungry was nowhere near to what was happening in Ukraine and Russia [0].

Also, after crash in 1990 Polish GDP was growing each year until 2020, but fertility rates keep on dropping until 2004. Then they stabilized below replacement rate.

GDP can not explain changes in fertility rate. There were cultural changes happening that had bigger impact.

[0] https://n-22-3.dcs.redcdn.pl/file/o2/tvn/web-content/m/orig/...

> the biggest reason why women decide to not have children is the perceived opportunity cost. Loosing on studies, career and freedom of being young

Agree. And not women only, males too. While a woman can decide to have a child completely on her own, it's most of the times a decision shared between parents. You need to take a multi-decades commitment that changes completely your life, permanently ties it with that at least two other people, and enormously reduces your space of freedom. It just doesn't make much sense.

>So exact opposite happened to what you predict.

No, it actually proves me right. The increase in job opportunities, which women definitely took advantage of, and adoption of modern western lifestyle is what made the birth rates plummet.

Since you mentioned former Soviet Union countries, Hungary implemented [1] new measures to give the people the necessary conditions to have kids. All the news articles I can find are from 2019, so it will take a while until we can decide if they had success or not:

[1] https://www.bbc.com/news/world-europe-47192612

In SU young women had essentially the same de facto 'opportunities' as young men, not withstanding certain society stereotypes. Actually it was illegal to be a 'housewife' (with some legal exclusions). That means - you have to work. After the birth of child and the period of state-mandated maternity leave (3 years in later period) you have to go back to workforce. So the motivation to study was to escape the grueling realities of kolkhoz or factory and achieve a better standard of living.

In fact the expectation was the both parents would be working and the child would be in childcare or kindergarten. Which of course put a lot of pressure on women due to reality of being a housewife and a full-time working woman at the same time.

There was also a lot of collective pressure - if you do not have a child by certain age you would be considered a failure, which is hard to attribute to communism per se but to certain backwardness and lack of education.

But I still think that big difference in fertility is the change from peasant family with 5-8 children to the urban family of 1-2.

I wonder if anyone would believe that for the last 40 years or so (and to this day) the accounting and HR have largely been woman-dominated professions in the Soviet Union/Russia?

Yeah, it is actually hard to believe that it may be otherwise in other countries. Also doctors - especially general practitioners.