Everyone that circumcises seems to think their age and way of circumcising are the best, but several national medical organizations are completely against circumcision.
I’ve been looking for years, but I’ve never been able to find a reputable source for either vitamin K or prothrombin levels peaking on the 8th day. Both seem to peak much later, with nothing special about the 8th day, and no other surgery would be scheduled for then. The source cited by an earlier answer seems to be a religious fundamentalist site, and the graphs don’t even spell “prothrombin” correctly.
Not all Jewish people believe in infant circumcision. Brit Shalom is an alternative naming ceremony to celebrate the birth of baby boys (and girls) to Jewish families. These are just some of the sites run by Jewish people opposed to infant circumcision:
See also https://www.youtube.com/watch?v=VJ8Kt6Vu4oE (footage of a bris with commentary from the subject)
https://www.youtube.com/watch?v=GVO6YzROkZE (Jewish man unhappy about being circumcised)
Many of the earliest intactivists, including George Wald, Suzanne Arms, Edward Wallerstein and Paul Fleiss, were Jewish.
“It is with the greatest hesitation, since I have no right and know so little, that I should like to suggest to my fellow Jews that perhaps the time has come to redeem the foreskin itself, rather than sacrifice it. Surely some substitute might be found for this rite, perhaps even involving a token drawing of blood from an older child, that would be preferable to this assault upon and mutilation of a newborn infant.”
“For it is a barbarous thing to meet a newly born infant with the knife, with a deliberate mutilation. And the part that is removed is not negligible; it has clear and valuable functions to perform. Not circumcising a boy will not only spare him a brutal violence as he enters life; it will promise him a richer existence. And that not only because the possession of a foreskin will increase his genital sensitivity and make possible more satisfactory and pleasurable sexual activity, but also because of the consideration with which this essay began: that the foreskin is the female element in the male.” George Wald (1906-1997), 1962 Nobel Prize
George Wald (1906-1997)
Jewish American scientist and Nobel Laureate (physiology/medicine)