If there is an afterbirth in the house, the house is ritually impure. That is, if a woman expelled an afterbirth without a sign of a fetus, we must assume that there was a fetus but it died and disintegrated after it emerged, transmitting ritual impurity of a corpse to everything in the house. Rabbi Shimon says, “The child disintegrated before it emerged from the mother. A dead fetus does not contaminate while it is inside the mother, and by the time the afterbirth appeared, the fetus was no more, so everything in the house is pure.”
To be considered afterbirth, it must have the size of no less than a hand-breadth. Incidentally, there are five laws where the measurement is a hand-breadth, and afterbirth is first. Also there is the shofar, which must be no less than a hand-breadth to be visible; a lulav – a palm branch taken on Sukkot, which must extend at least a hand-breadth over the other species; the walls of a sukkah, since we learned that a sukkah needs at least two full walls, and a third one no less than a hand-breadth; and a hyssop, used to purify a spiritual leper or the ritual impurity of a corpse.
Art: Jacobus Vrel - An interior of a house with a seated woman