How often should a woman examine herself to check that she is not a nidda?
The Gemara on today’s daf relates that Rabbi Zeira asked Rav Yehuda whether a woman should examine herself before engaging in sexual relations with her husband. Rav Yehuda responds that she should not do so, lest such an examination raise questions in her husband’s mind regarding her menstrual status, which may lead him to choose to refrain from intercourse.
From the presentation of Rabbi Zeira’s question it is not clear whether he is asking about performing an examination prior to intercourse or afterwards. The Rambam suggests that the discussion related only to an examination that takes place following intercourse, which is where we fear that the husband will be uncomfortable with the fact that his wife is checking her status at that time. Prior to intercourse, however, it is appropriate for a modest woman to make sure that she is in a pure state for relations with her husband. Rashi, Tosafot and others argue that Rabbi Zeira’s question applied to both before and after intercourse, and Rav Yehuda’s response was that such an examination would be inappropriate at either of those times.
This last approach is difficult, since the Mishna on tomorrow’s daf states clearly that women are encouraged to perform such examinations. In his Torat HaShelamim the Rema explains that Rabbi Zeira’s question was specifically about a woman performing the examination in front of her husband, for it is only in that situation that we fear that the examination may lead the husband to refrain from engaging in relations with her.
As far as the halakha is concerned, when dealing with a woman who has a set menstrual cycle and knows when to expect her menstrual flow, the Rema rules that the tradition is for the woman to refrain from performing such examinations both before and after intercourse (Shulḥan Arukh Yoreh De’a 186:1).