Circumcision can be a hazardous activity in two ways, according to recent daf yomi readings (Shabbat ch. 19). For one, Jewish observance and performance of the bris milah (= covenant through circumcision) may be persecuted by Gentiles. The Romans apparently sought to suppress bris milah, as indicated by our mishnah (bShab 130a)* and other rabbinic texts (e.g., the midrash Mechilta 20:6). Despite the persecution, rabbinic Judaism continued to require bris milah, sometimes at the price of martyrdom. The gemara deduces that circumcision is extraordinary for various reasons, such as the thirteen (1) covenants for which milah is done.
Of course, circumcision is hazardous in a second way -- as a physical, "medical" procedure. In my draft chart on risk in Jewish law, I see circumcision as a fascinating case because, depending on the circumstances, a bris may exemplify four different categories of risk:
(A) First, I label circumcision as a medium risk for newborns -- not the lowest probability of harm, and not necessarily fatal harm -- in the pre-Modern era. On 134a, the rabbis focus on bandaging, which if applied badly could disfigure the child's genitalia. Circumcision was a rather risky surgical procedure in antiquity and medieval times (cp. story of womana whose first 2 sons died, 134a Shabbat).
(B) Secondly, the Talmud also looks at elevated risk conditions for circumcision, as when an infant is too weak, too emaciated, or discolored. As a general principle. the mishnah states that a sick newborn is not circumcised until he becomes healthy. Specifically, the rabbis felt that the infant's color indicates a danger to their life (e.g., yellow = jaundice) may require postponement of the procedure (134a).
(C) Third, today, yellow skin tone is much less an indicator of actual danger to the baby. Instead, doctors can measure jaundice directly. Thus, today circumcision has become far less risky thanks to medical changes.** (Hence, here is where Jewish medical ethics adapts to a change in medical care. Contrast this situation with cases of where modern-era traditional rabbis feel that nature has changed.) DovBear tells an anecdote and poses a fine question: If a "yellowish" newborn is cleared by a doctor as ready for an immediate circumcision, should the Jewish father stay loyal to the medieval rabbinic authorities who cautiously require the postponement of the bris milah? Or, can our Jewish medical ethics (halakhah) waive the postponement, and thereby recognize and downshift to a lower risk based on modern medicine's ability to cure, prevent and remedy nearly any risks from circumcision for newborns?
(D) Fourth, the halakhah of circumcision also tackles an extremely low or implausible probability of harm. The Talmudic rabbis deal with the belief (or superstition) that an ominous wind may increase the risks to the infant (bYev 72b). Today, we are not inclined to credit a spooky wind as adding any marginal risk to the bris of an 8-day newborn. Indeed, I venture to say that many Rabbis themselves may not have considered the additional marginal risk as significant. After all, they judged it unnecessary to delay circumcision for any wind-related risk because "The Lord preserves fools" (shomer peta'im haShem) -- God protects us from dangers, at least dangers like inauspicious winds.
Although circumcision may illustrate rabbinic handling of these four different types of risk, I would emphasize that circumcision is unique and not illustrative. Almost no matter what the risk, throughout history Jews have felt commanded under Jewish law to take chances and perform the bris. In other words, circumcision is one of those actions that rabbinic law considers as highly unresponsive to the changes in risk conditions.
APPENDIX: Tractate Shabbat chapter 19 deals with much Talmudic medicine. For care of a circumcised baby, for instance, the Talmud discusses the use of cumin, salves, bandages, treatment of the wound, . In interpreting a mishnah, several rabbis insist that sabbath prohibitions may be overridden in order to bathe the baby's wound, as well as its entire body, because to refrain from a hot water bath is considered dangerous (saqanah) (134b). The Talmud also discusses androgynous babies (136b), babies with rare conditions ("suppressed" or absent foreskin) premature births and the danger facing premies (135a). The Talmud also contemplates whether, during its first 30 days of life, a newborn is deemed a safeqa, one of doubtful viability (136a), which leads into several aspects of fetal and newborn medical ethics. Feverish newborn (137a). Retakes w/a second circumcision procedure (137b).
* Rabbi Eliezer rules that, as an exception to the Shabbat laws, the Jew who will perform a bris, the mohel, may carry a concealed knife to the ceremony. R. Shimon b. Elazar categorizes the bris as a divine commandment for which "Israel sent themselves to death" (masru Yisroel atzman).
** A fierce dispute is raging among different Orthodox Jewish groups over a traditional part of the bris, the removal of blood by suction (metzitzah). As I revise this post, I will add links to this dispute here. Apparently, metzitzah administered directly by mouth exposes the newborn to the very low probability of a severe infection or contagion.
On the halakhah: Hirhurim: Metzitzah I (intro, R. Soloveitchik), II (RCA statement), III (view of R. Feivel Cohen), IV, V (RCA June 7), and VI (NY Times).
On the politics: DovBear re: Rabbi Moshe Tendler (and comments re: regulation), Yeshiva Ortho. The Canonist (e.g. Agudas Israel v. Satmar). Media links.
Volokh Conspiracy blog.
Current status of dispute (YO).