The reason there are fewer child births in the US since the 90s is mainly the reduction of pregnancies in the demographic “25 and younger”. They didn’t made a conscious choice, looking at their abacus and evaluating the state of the world. They slipped into it and were forced to make it work. Interestingly, they then still had children later in life as well, for more complex and personal reasons.

It seems to me, that if you give woman the choice, they choose not be pregnant at the cost of their career.