Hi
Congratulations!
You should submit the change in writing - not email. Notify them immediately that your daughter has arrived and that you will follow-up with other paperwork such as a birth certificate, passport, etc. as soon as it's available. Make sure to include your case number so there's no confusion.
If they haven't sent you the initial assessment, then it won't have any effect on the timing of your application.
1, You have to amend your and wifes IMM008 to show the child, amend the IMM5406 to include the child, a copy of the birth photos and the fee.
PMM