Is the belief that a visit from a menstruating or ritually impure woman to a woman in postpartum bleeding harms the newborn and causes it to be afflicted with "kabsah" a correct belief or a Bid‘ah (innovation)?

These matters are superstitions prevalent among common people, reprehensible innovations, and delusive omens. Benefit and harm are in the hand of Allah, and such matters have no effect whatsoever. The remedy for this is to rely upon Allah and say: "O Allah, there is no omen but Your omen, and no good but Your good, and there is no god other than You," and then proceed with one's need.