I think that is it. We have somewhat of a confirmation with Romania and Decree 770, which led to an increase in children (though that might have been temporary I'm not well versed in the history). I think there is no inherent desire to have children or if there is, it is far weaker than a lot of people think. And it makes sense, evolutionary. If you have a desire for self-preservation, a desire for the preservation of those close to you, a desire to nurture the young (once they are there, which also shows in seeing 'cuteness') and a desire for sex, then you don't really 'need' a desire for children directly, because the children will naturally follow from that chain of desires. It just fits with how evolution seems to works (I think at least), which often causes these daisy chains of things that work intermittently to cause something else.