Our Gemara on Amud Aleph discusses a dispute between Rabbi Akiva and Rabbi Yishmael regarding what benefits accrue for the woman who goes through the Sotah ordeal and is  proven innocent. The verse states, “And she shall be cleared, and shall conceive seed” (Numbers 5:28) but how far does this go?:

דְתַנְיָא וְנִקְּתָה וְנִזְרְעָה [זָרַע] שֶׁאִם הָיְתָה עֲקָרָה נִפְקֶדֶת דִּבְרֵי רַבִּי עֲקִיבָא אָמַר לוֹ רַבִּי יִשְׁמָעֵאל אִם כֵּן יִסָּתְרוּ כׇּל הָעֲקָרוֹת וְיִפָּקְדוּ וְזוֹ הוֹאִיל וְלֹא נִסְתְּרָה הִפְסִידָה

The verse: “And she shall be cleared, and shall conceive seed” (Numbers 5:28), indicates that if she was barren, she will be remembered and conceive a child; this is the statement of Rabbi Akiva. Rabbi Yishmael said to him: If so, all the barren women will seclude themselves with other men, and they will be remembered and conceive after drinking the bitter water and being found innocent; but that virtuous barren woman, who does not transgress the prohibition of seclusion, since she does not seclude herself with other men, she loses the opportunity to receive this blessing. (Even though the woman is innocent of adultery, she still purposefully committed the sin of seclusion and also caused God’s name to be erased for the ritual.)

אִם כֵּן מָה תַּלְמוּד לוֹמַר וְנִקְּתָה וְנִזְרְעָה זָרַע שֶׁאִם הָיְתָה יוֹלֶדֶת בְּצַעַר יוֹלֶדֶת בְּרֶיוַח נְקֵבוֹת יוֹלֶדֶת זְכָרִים קְצָרִים יוֹלֶדֶת אֲרוּכִּים שְׁחוֹרִים יוֹלֶדֶת לְבָנִים

Rabbi Yishmael continues: If so, what is the meaning when the verse states: “And she shall be cleared, and shall conceive seed” (Numbers 5:28)? This means that if in the past she would give birth in pain, from then on she will give birth with ease; if she gave birth to females, she will now give birth to males; if her children were short, she will now give birth to tall children; if her children were black, she will give birth to white children.

Tosafos raises an obvious question: Rabbi Yishmael’s questions that he asked on Rabbi Akiva could be asked on his opinion as well! If the benefit is to ease the birth pains for women who experience extremely painful labor, all women who have this condition will then seclude themselves with other men, and they will be rewarded with an easier labor after drinking the bitter water and being found innocent; but that virtuous barren woman, who does not transgress the prohibition of seclusion, since she does not seclude herself with other men, she loses the opportunity to receive this blessing?

Ben Yehoyada answers that since painful labor is not a constant condition, in that every labor and pregnancy is different even in the same woman, she would never voluntarily bring upon herself such humiliation of the Sotah ordeal . However, argues Rabbi Yishmael, the anguish of being barren could indeed draw a woman to purposefully provoke her becoming a Sotah so she could be found Innocent and thereby conceive a child as the reward.

I question this answer because it only resolves the first question of Tosafos, that women will falsely become Sotahs. However, Tosafos also asked, just as Rabbi Yishmael questioned the fairness for the woman who is modest and humble and does not get relief from her childlessness because she does not seclude herself on purpose to become a Sotah, unlike her peer who gamed the system and gets rewarded for it, so too he can ask on his opinion as well. How is it fair that the woman who suffers from painful labor does not get relief when a peer who is less modest does?  To me this is clear why Tosafos leaves this as an unanswered question.  

However, I will attempt an answer that might work for the second question of Tosafos. Though this is unusual, we could argue that the woman who goes through this humiliation and pain, achieves forgiveness as a result of her suffering even if self-inflicted. There is a concept in Jewish theology known as Teshuvas Hamishkal where a person inflicts pain commensurate with the pleasure he experienced from the sin.  (See Orchos Tzaddikim (26:80). Rav Yaakov Emden (Migdal Oz, Bais Hamiddos, Aliyyas Hadan Lekaf Zechus) uses a similar answer to explain why the Sotah who is found innocent merits any benefit when she at the very least engaged in suspicious behavior, which it is forbidden to do so because of the directive of not to even appear to be sinful, (as described in Mishna Shekalim 3:2). However, since she underwent such humiliation, her sins are forgiven.  We then may say that Rabbi Yishmael did not believe the miracle of becoming fertile is commensurate with the expiation of sin from the ordeal, while the smaller miracle of eased childbirth can be merited from the suffering and the forgiveness obtained in its account.