Sometimes, one may need to schedule a surgical procedure that will then require follow-up care involving the performance of various melakhot. Similarly, some procedures, such as the extraction of a wisdom tooth, cause pain for several days, which may impair one’s ability to enjoy Shabbat. If the surgery is not urgent, it is proper le-khatĥila to schedule it for the first three days of the week. However, if the best surgeon is only available during the second half of the week, the operation may be scheduled for then, even if it is possible to get an appointment at the beginning of the week with a less expert surgeon (see above, 2:10-11).
If a woman is due to give birth and her doctors decide that labor should be induced, it may be done on Friday, even though it is reasonable to assume that this will cause her to give birth on Shabbat (SSK 32:33 and the notes).
If an operation is urgent, it should not be postponed, even if it is possible to postpone it until the beginning of the week. This is because sometimes problems arise, and the surgery may be delayed beyond the time that is medically desirable.
If a baby boy was sick and his circumcision was delayed, poskim disagree whether the circumcision may be held on a Thursday or Friday. Some argue that since it has already been postponed beyond the Torah-mandated eighth day, the baby should not be circumcised on Thursday or Friday, because in the days following the circumcision he might require care that would involve Shabbat desecration. This is the custom in many Sephardic communities (Tashbetz 1:21; Rav Pe’alim, YD 4:28; Yabi’a Omer, YD 5:23). Others maintain that the likelihood of needing to desecrate Shabbat following the circumcision is not high, and since there is a mitzva to perform the circumcision as soon as possible, one should do so even on Thursday or Friday (Shakh, YD 266:18; MA 331:9). This is the widespread custom among Ashkenazic and Yemenite Jews, as well as some Sephardim.