I came across an argument against the immaculate conception of Mary. Though, it may not have been exactly that. More precisely, it was argued that the belief in the immaculate conception was inconsistent with the belief that Mary is the woman described in Revelation. In short, the woman described in Revelation has birthing pains. Birthing pain is a consequence of original sin. Mary had no original sin. Hence, either the woman described in Revelation is not Mary, or Mary had original sin.