When someone is about to be a parent (I think this question stick more to a man than a woman, considering the empathic link that's been biologicaly created between a child and his mother) is he really asking himself: Will they worth it ?

I think the situation is very different planned vs. unplanned. For me, once the decision was made I had no second thoughts. Also, the little munchkins re-write you emotionally once they arrive <- no one told me about this, so it was actually a bit of a shock.