Nixon took USA off the gold standard in 1971 and then fertility rate started to drop, people got sicker and women had to start working to feed the family.
Discussion
Coincidence, other forces were much more impoortant
What were the other forces?
The extreme expansion of the monetary supply 1914-1971 caused a massive growth of the state, it imposed a too big burden in taxes and regulation. Humans, society and the economy is very plastic, but there are limits. Cutting the ties to gold probably became a release valve, and in fact the expansion of the monetary supply gradually (but bumpy) came down a little bit.
Exactly. You both are talking about the same.
Money supply increased. Families got debased. Families became poorer. Which impacted fertility rates. And Gold became the release value.