Three months is sufficient time to know whether the widow is pregnant from her first husband, for after three months her pregnancy can be seen. The scholars asked: It should be sufficient to wait only a few days after the death of her first husband.
Then she could get remarried, and three months after the death of her first husband her belly and her breasts, which show pregnancy-related changes after three months, could be checked. If they do indeed show such changes, then she is pregnant by her first husband. Answer: Since she is married, it is inappropriate and an embarrassment to her if others examine her, with her belly and her breasts exposed to them.
The scholars went on to ask: There is a modest way to check whether she is pregnant. She should walk over loose moist sand, for the steps of a pregnant woman are heavier, and this can be seen in her footprints.
Therefore the woman would try to walk lightly, like a woman without a fetus in her belly, so that none could discover her pregnancy. Why did the early sages rule that a man should not wed a pregnant widow or divorcee? Answer: The early sages forbade marrying a pregnant woman lest she become pregnant again during her pregnancy and the new fetus press upon the older and cause it harm. The scholars asked: Then each man should be forbidden to have sexual relations with his pregnant wife lest she become pregnant again and cause harm to the older fetus.
Answer: The fear is not that she will become pregnant again, because we rely upon G-d to have mercy and protect the fetuses. The fear is that the second husband will cause harm to the fetus during sex.
