Having children is not a choice, it is a matter of survival. Below replacement fertility is a real problem with so far unknown results. You do end up in a hole

Having children is not a choice, it is a matter of survival. Below replacement fertility is a real problem with so far unknown results. You do end up in a hole where "it is a choice but everyone who takes it is penalized" is the actual result. (at least for some time) If it is out beneficial, it is not a choice anyway or one only rich can afford. You said it yourself.