1) CONTRACEPTION
OPINIONS: The Beraisa teaches that three types of women use a Moch during relations (see Insights to Kesuvos 37:1) -- a minor, a pregnant woman, and a nursing mother, because pregnancy poses a danger to their health.
Is the use of a Moch permitted only in these cases due to the danger involved, or is it permitted even when no danger is involved?
(a) RASHI (DH Meshamshos) writes merely that "these women are permitted to use a Moch, and they are not considered as though they are destroying Zera." According to the RITVA's text of Rashi's comments, Rashi adds, "We permit this to them because of the danger to her and to her child." The Ritva understands that Rashi means that although the use of a Moch is generally forbidden because of the prohibition against Hashchasas Zera, in this case it is permitted due to the danger posed to the woman by pregnancy.
(REBBI AKIVA EIGER (Teshuvos 1:71, DH ul'Zeh) infers from Rashi's words, "and they are not considered as though they are destroying Zera," that an adult is generally prohibited from using a Moch because it destroys the man's Zera. Rebbi Akiva Eiger asserts that Rashi disagrees with RABEINU TAM (quoted by TOSFOS to Yevamos 12b, DH Shalosh, and Tosfos to Sanhedrin 59b, DH v'Ha, as cited here by the GILYON HA'SHAS), who maintains that a woman is not included in the prohibition against Hashchasas Zera since she is not included in the Mitzvah of Piryah v'Rivyah.)
1. The Ritva questions Rashi's explanation. The Gemara states that a girl under the age of eleven may not use a Moch. Rashi (DH Pachos) explains that she may not use a Moch because she is too young to become pregnant, and thus there is no allowance for her to cause Hashchasas Zera. The Ritva asks that if a young girl cannot become pregnant, why is she prohibited from using a Moch? The Zera will be destroyed whether or not she uses a Moch, since in any event she will not become pregnant.
The BEIS MEIR (EH 23) answers this question. He explains that although a girl under the age of eleven cannot become pregnant, having relations while wearing a Moch is considered equivalent to having relations in an unnatural manner (the manner of Er and Onan; see Bereishis 38:7-10, Yevamos 34b) and is considered Hashchasas Zera.
2. The Ritva asks further that according to Rashi, the Rabanan who disagree with Rebbi Meir (as quoted later in the Beraisa) maintain that these three women may not use a Moch. Why, though, do they require that a woman put herself in danger by not protecting herself simply because of the reasoning of "Shomer Pesa'im Hash-m" -- "Hash-m protects the fools" (Tehilim 116:6)?
The answer to this question may be inferred from the words of the KOVETZ SHI'URIM (#136). The Kovetz Shi'urim writes that the principle of "Shomer Pesa'im Hash-m" means that a person may conduct himself normally and not worry that he will be harmed, if acting in a way which would avoid harm would be an unusual way to act. The Kovetz Shi'urim proves this from the Gemara in Avodah Zarah (30b) which states that one is permitted to eat a fig or grape at night and he is not required to examine it (as he must do during the day) to ensure that it contains no snake poison. Why is the Gemara lenient with regard to examining a fruit for poison, when one must do everything in his power to prevent danger to life? Why does the Gemara not require him to wait until daytime to eat the fruit? It must be that a person who conducts himself in a normal manner is protected by Hash-m whenever there is no normal, alternative form of conduct at that time.
This explanation answers the Ritva's question on Rashi. The Gemara in Avodah Zarah applies the principle of "Shomer Pesa'im Hash-m" in a case of Piku'ach Nefesh when it is the normal way of conducting oneself. Similarly, a woman for whom pregnancy poses a danger may live with her husband in the normal manner and rely on Hash-m's assurance of "Shomer Pesa'im Hash-m."
The TORAS CHESED (44:2) writes that according to the Rabanan, the probability of mortal danger to which these women are subject is negligible. When the probability of danger is so low, they may rely on "Shomer Pesa'im Hash-m," and thus the use of a Moch is forbidden.
(b) The RITVA and TOSFOS (DH Shalosh) explain that these three types of women are obligated to use a Moch (according to Rebbi Meir). The Rabanan permit them to use a Moch but do not obligate them, because they may rely on "Shomer Pesa'im Hash-m." (D. Bloom, Y. Montrose)

39b----------------------------------------39b

2) IS THE KESUVAH MID'ORAISA OR MID'RABANAN?
OPINIONS: The Beraisa states that although a man who rapes a woman is obligated to pay the fine immediately, if he dies after he marries her but before he pays the fine she does not receive a Kesuvah, according to the Rabanan. The fine which his heirs must pay to her takes the place of payment of the Kesuvah. Rebbi Yosi b'Rebbi Yehudah disagrees and rules that she receives a Kesuvah of 100 Zuz (the amount a Be'ulah receives as her Kesuvah).
The Gemara explains the reasoning of the Rabanan. The enactment of Kesuvah was instituted in order to cause a husband to pause and ponder before he divorces his wife. It follows that a man who was required by the Torah to marry the woman he raped should have no obligation of Kesuvah, because the Torah forbids him from divorcing his wife (Devarim 22:19). Rebbi Yosi, on the other hand, maintains that the man might make his wife so miserable that she will invite him to divorce her (in which case he must divorce her; see SHULCHAN ARUCH EH 177:3). Accordingly, the enactment of Kesuvah applies.
The Gemara's question, "Why did the Rabanan establish a Kesuvah?" implies that the obligation to give a Kesuvah is mid'Rabanan. This, however, is subject to dispute.
(a) The SHITAH MEKUBETZES quotes RABEINU TAM who asserts that the Kesuvah of a Besulah is mid'Oraisa. The Gemara here is discussing a woman who was raped and is not a Besulah, and thus the Kesuvah to which it refers is not mid'Oraisa.
The Shitah Mekubetzes questions the explanation of Rabeinu Tam. It is possible that a man rapes a woman in a way that leaves her a Besulah (i.e. she'Lo k'Darkah) and yet all of the Halachos of rape apply to her (e.g. the rapist must pay a fine and marry her). In such a case her Kesuvah is mid'Oraisa, but the Gemara implies that in all cases of rape the Kesuvah is only mid'Rabanan. (See also TOSFOS (DH Taima Mai) who asks this question but gives no answer.)
The Shitah Mekubetzes answers that according to the Rabanan and Rebbi Yosi, no girl who is raped receives a Kesuvah mid'Oraisa, regardless of whether she is still Besulah. This is because the verse states with regard to the fine of one who seduces a woman, "Kesef Yishkol k'Mohar ha'Besulos" -- "he must pay money like the presents of the Besulos" (Shemos 22:16), which means that the fine which a woman who is raped or seduced receives is in place of her Kesuvah mid'Oraisa. This is why the Gemara's discussion here involves only why the Rabanan enacted that a Be'ulah also receives a Kesuvah. The PNEI YEHOSHUA gives a similar answer and cites support from the Mechilta which implies that the verse teaches that the Kenas is in place of her Kesuvah.
(b) RABEINU CHANANEL maintains that even the Kesuvah of a Besulah is mid'Rabanan. His view is consistent with the words of the Gemara here. The ROSH (1:19) quotes this opinion in the name of the GE'ONIM and discusses both opinions at length. (See Insights to Kesuvos 10:1.) (Y. Montrose)