In the west, taxes were raised to pay for the welfare state. This reduced the amount of money available for people to spend on themselves and their families. So, the mothers were sent out to work and they were taxed as well. Then they also have to pay for childcare too. So that reduces the incentive to have children. Couples are having children later in life because it takes longer to get to a point where the family can get by on one wage. This reduces the amount of time available on the biological clock to have more children and the mother is anxious to get back to work so the family can catch up financially. What the designers of the welfare state forgot were that children have always been necessary to provide care for the old. The only difference is whether that was directly through families, or indirectly through taxes. The thing is, the welfare state adds a layer of bureaucratic parasites that has to be paid for as well. Most working mothers I know (including my wife) would rather be home with their kids than working. At least for the first few years anyway.