Isn't fertility a simple economic explanation? With high fertility rates each successive generation is a multiple larger than the one before it, and then again

Isn't fertility a simple economic explanation? With high fertility rates each successive generation is a multiple larger than the one before it, and then again on endlessly. And schools, nurseries, and every other centure would also be exponentially growing - even pediatricians and their reliable stack of baby books. Basically it would just be a huge market with massive potential reach, and one that would be growing constantly, and with basically 0 barriers to entry.