What is the ruling on a husband attending his wife's childbirth without necessity, and has there been any religious prohibition regarding that?

There is no hadith that prohibits a man from being with his wife during childbirth or other times. However, good manners and conduct necessitate that a man avoid being present in such a situation if his presence is not needed, based on the Prophet’s (peace be upon him) saying: "Wait until you enter at night - meaning for supper - so that the disheveled woman may comb her hair and the absent one may use depilatory."