what is logic of iddah after saying talaq - as you see, it is not just to know out, whether the wife has baby, but it is also because the husband may change his mind, because he may lose his wife after iddah, and allah has ordered that waiting term (iddah), this is why i think that waiting the iddah after saying talaq is required even for husband at 3rd divorce and he already has 4 wifes. (alternative logic is that if a man has 4 wifes and divorces one of them [with intention] to marry another woman, in case it is the "3rd divorce" with her, since he cannot take the wife back, he need not wait the iddah, and so he can quickly marry another woman). and 3 menstruations are not needed to check whether wife has baby, this also proofs that it is probably also time to think. (is there other function of 3 periods?)
