Q. My granddaughter was born a couple of days ago and I want to know can my husband go to shul and name her. My daughter and son-in-law go to Conservative and are going to name her in a month's time?
A. Poiskim and minhogim disagree as to which one of the parents has the right to name a newborn and which is then the correct future sequence to follow (Ramban, Daas Zkenim Bereishis 38,4 – Shaar Hamilah 80, et al.). However, they all agree, that giving a name is the prerogative of the parents only.
There are different traditions as to when to give the name to a daughter. They vary from immediately, first Krias Hatorah, the first Shabbos, two Shabbosim or to waiting a month, as the lunar cycle is symbolic of females, (see Seifer Habris Ch. 6 – Minchas Ytzchok 4, et al.), most prevalent is the first occasion of the reading of the Torah or waiting for the first Shabbos.
A grandparent could name the baby, with the consent of the parents and acting on their behalf.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit"a