סימן קנד סעיף ג
וְיֵשׁ נָשִים, שֶׁאֵין לָהֶן יוֹם קָבוּעַ לִרְאוֹת, לֹא בִימֵי הַחֹדֶשׁ, וְלֹא בְהַפְלָגוֹת שָׁווֹת, אֲבָל יֵשׁ לָהֶן סִימָנִים בְּגוּפָן, כְּגוֹן שֶׁדַּרְכָּהּ הִיא, שֶׁקֹּדֶם רְאִיָתָהּ הִיא מְפַהֶקֶת, דְּהַיְנוּ, כְּאָדָם שֶׁפּושֵׁט זְרוֹעוֹתָיו מֵחֲמַת כֹּבֶד, אוֹ כְּאָדָם שֶׁפּוֹתֵחַ פִּיו מֵחֲמַת כֹּבֶד, אוֹ כְּאָדָם שֶׁמּוֹצִיא קוֹל דֶּרֶךְ הַגָּרוֹן מֵחֲמַת הַמַּאֲכָל שֶׁאָכַל, כָּל אֵלּוּ עִנְיָנֵי פִהוּק הֵן. וְכֵן אִם מִתְעַטֶּשֶׁת דֶּרֶךְ מַטָּה אוֹ דֶּרֶךְ מַעְלָה, אוֹ מַרְגֶשֶׁת אֵיזֶה מֵחוֹשׁ נֶגֶד טַבּוּרָהּ אוֹ בְּבֵית הָרֶחֶם, אוֹ שֶׁאָחֲזוּהָ צִירֵי הַקַּדַּחַת, אוֹ סָמְרוּ שַׂעֲרוֹת בְּשָׂרָהּ, אוֹ שֶׁרֹאשָׁהּ וְאֵבָרֶיהָ כְּבֵדִים עָלֶיהָ, כֹּל שֶׁהֻחְזְקָה שָׁלֹשׁ פְּעָמִים רְצוּפוֹת שֶׁבָּא לָהּ אֶחָד מִן הַמִּקְרִים הַנִּזְכָּרִים, וְאַחַר כָּךְ רָאֲתָה דָם, הֲרֵי זוֹ קָבְעָה וֶסֶת, וְזֶה נִקְרָא וֶסֶת הַגוּף. וְדַוְקָא פִּהוּק וְעִטּוּשׁ כַּמָּה פְעָמִים זוֹ אַחַר זוֹ הֲוֵּי סִימָן וֶסֶת, וְקָבְעָה בָּהֶם. אֲבָל מִשּׁוּם פִּהוּק וְעִטּוּשׁ פַּעַם אַחַת, אֵין הַוֶּסֶת נִקְבָּע, כִּי זֶה דֶרֶךְ כָּל הָאָדָם. וְדַוְקָא שֶׁקָּבְעָה כָּל שָׁלֹשׁ הַפְּעָמִים עַל יְדֵי מִקְרֶה אֶחָד. אֲבָל אִם פַּעַם בְּמִקְרֶה זֶה וּפַעַם בְּמִקְרֶה זֶה, לֹא הֲוֵי קְבִיעוּת.
There are some women who do not have an established date of perception, neither of the days of the month, nor of equal intervals, but do experience various physical symptoms.2That are brought on by the oncoming menses. For instance, it is charactaristic of her to yawn before menstruation, in the manner of one who stretches his arms from weariness, or like a person who opens his mouth (yawns) from drowsiness, or like a person who burps because of the food he has eaten—all of these are included in "yawning." Similarly, if she flatuates or sneezes, or feels some pain in the region of the navel or the womb, or she has an attack of chills and fever, or the hair of her body bristles, or her head and (her) limbs grow heavy. If she experienced any of these symptoms, on three consecutive periods, and immediately began menstruation, this symptom serves as her established date of menses. And this is referred to as "Menses regulated by physical symptoms."3During the onset (day or night) when she experiences one of these symptoms, she is forbidden to you. Shulchan Aruch 189:19. At that time she must examine herself to see if she is menstrually clean. Eshkol 34. If she did not examine herself, she remains forbidden until she does and finds herself menstrually clean. See Shulchan Aruch 184:9. Yawning and sneezing only when repeated many times consecutively are regarded as symptoms by which to establish a date of menses, but if she yawns or sneezes one time, the date of menses is not established for it is a natural and normal thing. The date of menses is established by symptoms only if she perceived each of the three times through one particular symptom. But if once it occurs through one symptom and once through another symptom, it is not considered established.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)