18-20 is the typical age for the most healthy children, and lowest maternal problems. At the same time, economic health doesn’t peak until well into the 40s. EDIT: For those wanting to get pedantic about the exact age ranges, you’re missing the point. Economic, mental, and physical capabilities are massively misaligned in our current society, on a global scale.
It makes for a social tug of war that’s never easy to handle.
If you lose more than water weight in 3 days, it’s probably due to traumatic illness or amputation.