When learning the Mishna (33b) we were introduced to the concept of havana (literally “a period of distinction”), which is a period of time that we obligate a woman to wait before getting married when it is necessary to clarify whether she is already pregnant from another man. According to a baraita quoted on our daf, Rabbi Yehuda also applies this rule to the cases of women who convert, are freed from captivity, or are released from slavery. In all of these cases, Rabbi Yehuda rules that we must be concerned that these women engaged in sexual relations in their former situations – perhaps against their will – and thus may be pregnant. Therefore, we obligate them to wait three months before they can marry. Rabbi Yose, on the other hand, permits them to marry immediately.
Rabba explains Rabbi Yose’s position by saying that since these are all cases where the woman does not want to become pregnant, she will likely use a mokh – an absorbent barrier in her vaginal canal that will keep her from conceiving. Abaye objects that this will not work in all of the cases. The woman who was a captive, for example, could not possibly be able to prepare herself in such a way before she was raped. Abaye suggests that Rabbi Yose relies on the fact that the women turned themselves over in order to keep the semen from fully entering, so we need not be concerned that they became pregnant. Rabbi Yehuda is concerned that they do not turn themselves over well enough, and they may become pregnant anyway, their best efforts notwithstanding.
From a medical standpoint, “turning over,” as described by Abaye, would have no effect whatsoever on the chances of pregnancy. It is likely that Abaye’s intention is not simply for the women to turn over, but to take all possible preparations in order to avoid pregnancy, including herbs, drugs and so on. Rabbi Yehuda’s concern is that there are few methods that can be used at the conclusion of sexual relations which can guarantee that no pregnancy will result.