Please G-d we are expecting a baby soon. We know that if it is a boy then we can't tell anyone his name until the Bris. But why? And if it is a girl, she is meant to be named in synagogue before the name is announced, is that right? What is the significance of all of this?
Naming is a big thing. A child's Hebrew name is the description of their soul, their mission and their spiritual energy. Only when the name is given does the soul settle in the body. And so we give the name at the earliest opportunity, but also at the most spiritually suitable time.
For a boy, we wait for the Bris. We want him to receive his name after entering into the covenant with G-d. But for a girl, there is no need to wait. At the very next Torah reading after her birth, her father (or if necessary someone else) is called to the Torah, and the rabbi then says a prayer to bless the mother and name the baby. Some have the custom to wait until the first Shabbos after the birth, but it can be done before that on a Monday or Thursday morning when the Torah is read.
The reason we don't reveal the name before the actual naming is because we want her name to 'land' on her in an aura of sanctity and holiness. This is why we do it at the Torah, in synagogue. Such an occasion has similar holiness to a Bris. The soul of Elijah the Prophet is present at every girl's naming too, to bless the child and approve her name. We despatch this freshly born soul on her life mission surrounded by holiness and blessing.
Apart from the naming ceremony which is done soon after the birth, the parents should hold a Kiddush, a celebratory meal, in synagogue on a Shabbos day, some weeks after the birth of a girl, as a thanksgiving to G-d for her safe arrival.
If a girl was born but not named at the Torah, it is never too late. Even an adult can have a naming ceremony done for them, and hold a Kiddush to celebrate. This can only bring blessing, and who doesn't need more blessing?