Halakhah for Keritot 27:23
והקתני
Does he not deal with the Day of Atonement, where the requisite standard quantity is the size of a date, and a date corresponds to two olive-sizes? - Said R'Zera: He ate of a kidney together with the heleb attached thereto.<span class="x" onmousemove="('comment',' I.e., he ate one olive-size of the kidney and another olive-size of the heleb. For the latter he is, under the conditions mentioned in the Mishnah, liable to three sin-offerings and a guilt-offering; when followed by an olive-size of the kidney he complements the date-size required for the transgression of the Day of Atonement, which provokes the fourth sin-offering. R. Zera's view is that the Tanna of the Mishnah wishes to confine himself to the eating of one olive-size of heleb, while in the combination of piggul and nothar it would be necessary to assume that two olive-sizes of heleb have been consumed (Rashi) .');"><sup>13</sup></span>
Torat HaAdam
We allow a pregnant woman to eat repeated small portions that are each below the minimum forbidden size, because she is in danger. This ruling is queried; if she is in danger, let her eat more. Rav Papa said the correct reading is: We allow a pregnant women to eat repeated small portions, and even more if she is danger. (BT Keritut 13a)
This means that even if she needs a full [forbidden] quantity, we feed her in repeated small portions so that it does not add up to the full amount within a short time16 halakhically defined as the time span within which the total forbidden quantity is deemed to accumulate. Thus rules the author of Halakhot (Sefer Halakhot Gedolot – at the end of the Yom Kippur Laws). It seems to me that this applies to a sick patient as well, sparing him from eating quantities that would normally be punishable by karet or flagellation. You may wonder then why the Talmud says you feed the patient with the minimum infringement of the law, choosing tithes where there is a choice between un-tithed food and tithe, both of them being simply forbidden17with equal punishments. In cases where eating the full quantity of different foods would lead to punishments of different severities, where the patient eats less than the punishable quantity eating the one food is considered more serious than eating the other. Another approach is to say that the Talmud refers to the case of the sick patient who is estimated to need a full quantity within the specified [normally punishable] time.18Therefore the ruling is to give the less forbidden food rather to give the food in small quantities.