This article is an excerpt from our Sefer
2. When feeling hungry or satiated:
[Due to medical reasons, as well as due to negative effects on a child born from such a union] one is not to have intercourse when he [or she] is hungry or satiated [right after a meal]. Rather, one is to do so [some time] after eating, when the food has already begun to be digested [half-way to the point that he is no longer full, but also, not yet hungry]. [This applies to both the husband and the wife. This applies even if one’s wife cannot currently conceive, such as during pregnancy, and it most certainly applies if there is possibility of conception. Seemingly, this adherence is not a letter of the law obligation, but rather a medical and practical advisory.]
Eating a proper diet prior to intimacy:
Being that the seed of man is developed from the foods which he eats, it is proper that one be careful to eat light and healthy foods on the day of intimacy, and that he does not overeat. Eating coarse foods will affect the quality of the seed and can cause the children to carry damaging character traits. Accordingly, the foods that one eats on the day of intimacy should also be regulated, this is included in the Mitzvah of Kedusha during Tashmish. Certainly, one who accidentally ate a non-Kosher food should not have intercourse on that day due to this reason, as the sperm created from such foods will be impure and contain evil tendencies. It is for this reason that the laws of childbirth brought in the beginning of Parshas Tazria follows the laws of Kashrus found in the end of Parshas Kedoshim.
 Michaber 240:15; Tur 240:15 and E.H. 25:2; Rambam Dei’os 5:4; Igeres Hakodesh of the Ramban Chapter 3; See Siddur Ya’avetz Mosach Hashabbos Mitos Kesef 4:1-2 part 2 and 7:2; Taharas Yisrael 240:82; Kaf Hachaim 240:88; Piskeiy Teshuvos 240:27; Sheyikadesh Atzmo [Nachmonson-2015] p. 377
 Kitzur SHU”A 150:15; See coming footnotes
 The reason: One is not to have intercourse when hungry, as this can cause the child to be weak and dull headed. Likewise, one is not to have intercourse when one is satiated after eating, doing so can cause the child to be Megusham, as the seed will derive from the waste products of the food and will cause the child to have difficulty in comprehension and a stone heart. [Kesef Mishneh Dei’os 5:4; Igeres Hakodesh of Ramban 1-3; Chesed Le’avraham Mayan 4:11; Elya Raba 240:22; Pela Yoeitz Zivug; Siddur Ya’avetz ibid and 4:3 that if the seed is too warm from the food then the child will have an angry temperament, and if from cold seed due to hunger, he will be stupid; Kaf Hachaim 240:88; Piskeiy Teshuvos ibid; Sheyikadesh Atzmo 33 footnote 1] It can also cause the child to have very bad character traits such as anger. [Ramban ibid] Likewise, it is unhealthy for the person to have intercourse when hungry or satiated after a meal, independent of the possible effects on the child. [Kesef Mishneh ibid; Piskeiy Teshuvos ibid]
 Siddur Ya’avetz Mosach Hashabbos 7 1:2; See Sheyikadesh Atzmo 33:2
 Pela Yoeitz Zivug; Sheyikadesh Atzmo 33:1 footnote 1; However, from the Kesef Mishneh, and Poskim ibid, it can be implied that this adherence applies mainly to the husband and not the wife.
 See Kesef Mishneh ibid in previous footnote; Piskeiy Teshuvos ibid; Sheyikadesh Atzmo 33:1 and 3
 Igeres Hakodesh of Ramban Chapters 3 and 4; Siddur Ya’avetz Mosach Hashabbos Mitos Kesef 5:1
 Ramban ibid; Siddur Ya’avetz ibid