לזכות אבי מורי ואמי מורתי שיחיו
A person should always act within the framework of nature. If he does so then he will be protected. As the Gemara [Yevamot 12b]:
תני רב ביבי קמיה דרב נחמן שלש נשים משמשות במוך קטנה מעוברת ומניקה קטנה שמא תתעבר ושמא תמות מעוברת שמא תעשה עוברה סנדל מניקה שמא תגמול בנה וימות
Rav Beivai taught a braisa before Rav Nachman: Three women may engage in relations with a contraceptive resorbent, a soft fabric placed at the entrance to their wombs to prevent conception, despite the fact that this practice is generally prohibited. They are as follows: A minor, a woman who is already pregnant, and a nursing woman. The braisa specifies the reason for each exception: A minor may do so lest she become pregnant and perhaps die; a pregnant woman, lest she be impregnated a second time and her previous fetus becomes deformed into the shape of a sandal fish by being squashed by the pressure of the second fetus. As for a nursing woman, she does so lest she become pregnant and her milk dry up, in which case she will wean her son too early, thereby endangering him, and he will die.
ואיזו היא קטנה מבת י"א שנה ויום אחד עד י"ב שנה ויום אחד פחות מכאן ויתר על כן משמשת כדרכה והולכת דברי ר"מ וחכ"א אחת זו ואחת זו משמשת כדרכה והולכת ומן השמים ירחמו משום שנאמר (תהלים קטז, ו) שומר פתאים ה'
Who is considered a minor? It is a girl from the age of eleven years and one day until the age of twelve years and one day. If she was younger than this or older than this, she may go ahead and engage in relations in her usual manner. This is the statement of Rabbi Meir. Since it is assumed that a minor who is less than eleven years old cannot become pregnant, she is considered to be in no danger. And the Rabbis say: Both this one and that one, i.e., in all these cases, she may go ahead and engage in relations in her usual manner, and Heaven will have mercy upon her and prevent any mishap, since it is stated: “The Lord preserves the simple”(Psalms 116:2).
Explains the Rogochover that this rule that people are guarded when they follow the natural course of events only applies when the danger is a natural one. But when the danger is not natural, he [or she] will not be protected. In the words of Rabbeinu:
"רק בדבר דכן מציאות התולדה אמרינן גדר מן השמים ירחמו וגדר שומר פתאים ה' .... אבל כל דבר שאין זה גדר הטבע רק סיבה בודאי חילוק ואסור".
Therefore, when a woman is ill and getting pregnant will constitute a danger for her, she may not have relations because she won't be protected. ['שו"ת שלמת יוסף ל]
