We learn that according to Rav Bibi kamei deRav Nachman, a pregnant woman is meshameshet with a moch, because of the fear that the baby would degenerate into a "sandal". I think we must understand that the effect of the moch is to block the zera or (according to Rabeinu Tam) to absorb the Zera, so that a "sandal" is not created by the zera being accepted into the woman. But once a woman is pregnant, there is no egg to be fertilized (a pregnant woman cannot become pregnant "again"), so why should the moch have any effect? Must we resort to "nature has changed", or is there a more simple pshat? Why should a "sandal" have anything at all to do with whether or not the woman uses a moch? Also, would this statement (that a pregant woman uses a moch) have any practical hallachic significance today?
Daniel Moskovich, Copenhagen, Denmark
Yours is Tosfos' question on Rashi's explanation. Tosfos' suggestion is that the Moch does not prevent a new conception. Rather, it prevents the Zera from causing one of the fetuses in a tightly-packed womb from being damaged by the force of the Zera and becoming a "Sandal".
Be well,
Mordecai Kornfeld
There are cases in the medical literature of second pregnancies conceived during a pregnancy. Though improbable hormonally it can happen and even has happened with 2 different fathers ch'v.
Thank you for your forum,
Rabbi Michael Goldrich, MD