Q. If you want to make a mi sheberach for the baby, can you give him a name before the brith? When and how do you do it? and if not, what name do you use?

A. A number of consequential and significant reasons are mentioned for naming the newborn at the bris ceremony (Klolei Hamilo p.94) also Avrohom Ovinu was given his full name only after he circumcised (ibid.)

However, if the child was born premature or is ill, some Poskim maintain that he could be named before the bris, to permit praying for him (Oz Nid’bru 7: 73)

Horav Shlomo Miller’s Shlit”a opinion is that it is better not to deviate from the norm of giving the name at the bris. When reciting the mi sheberach and other tefilos, one should mention just “tinok”, (infant) ben followed by his mother’s name.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a