Hungarian Poskim were prominent among those who considered Metzitza ּB’Peh as an integral part of the Mitzvah of Milah. For example, the Maharam Shick (Orach Chaim 152) in his responsa goes as far as claiming it’s a Halacha L’Moshe MiSinai! This statement had far-reaching ramifications. It would mean that no Metzitza B’Peh implies no fulfilment of the Mitzvah of Milah. This view is now common.
The problem with this approach is that I don’t think anyone actually agrees with it, and here I include those who follow the Maharam Shick (who incidentally made this claim even though his teacher, the Chasam Sofer did not).
What happens when there is a Bris performed by a Charedi Mohel who normally performs Metzitza for members of his kind, and that Bris is for say a non-frum (or “overly modernishe” orthodox) couple? I’ve been at such Brissen, and I’m sure many of you have as well. Guess what. There is no Metzitza B’Peh. Some estimate that 90% of Brissen in Israel amongst this group do not have Metzitza B’Peh even though the Bris is performed by a Charedi Mohel. If it is Halacha L’Moshe MiSinai, how can that be? Isn’t the Mohel transgressing the Torah prohibition of misleading the blind?
Ergo, we just don’t accept the view that it’s Halacha L’Moshe MiSinai. I think it’s that simple.
What is Halacha, however, is never to enter into Safek Pikuach Nefesh. That’s why they did Metzitza in the first place and that’s why it’s no longer necessary!