2,129. A "Sandal" and a Placenta

Hilchos Issurei Biah 10:12

Sometimes the blood remaining from the formation of a fetus congeals into a shape like the tongue of an ox. This is wound around part of the fetus and is called a “sandal.” A sandal never forms without a fetus; a similar mass of blood without a fetus isn’t called a sandal. Most fetuses don’t have a sandal. If a pregnant woman is struck on the stomach, injuring the fetus, it may become like a sandal. Sometimes it retains facial features and sometimes it dries up, altering in appearance. Blood from elsewhere can then congeal on it, obscuring the facial features. Subsequently, if a woman expels a male fetus and a sandal, she observes the rules that follow the birth of a boy and a girl because the sandal might have been a female fetus. We rule stringently in this matter and assume the mother to be unclean from another fetus even in the absence of facial features because she is already unclean from the fetus that she definitely expelled.

Hilchos Issurei Biah 10:13

The fetus forms inside a thick membrane that resembles goatskin. This membrane, which surrounds the fetus and the sandal when there is one, is the placenta. When it’s time for the fetus to come out, it rips through the placenta. When it starts to form, it resembles a woof thread that’s hollow like a trumpet and thick like a chicken’s crop. A placenta must be at least a handbreadth (about 3”) in order to impart ritual impurity.