Best period of time
The best time for the newborn session is 4-14 days after birth, overdue babies up to 1 week. Why so short period of time? Babies are more sleepy first couple weeks after birth, later they become more curious, sleeping less and less, staying awake longer period and it might be very difficult and sometimes even impossible to do posed sleepy newborn photos. Babies also changing very fast and good to capture them when they just come to the world, in a month you baby will be looking different than right after you saw him or her 1st time.
Usually, I recommending to reserve a session for your baby before the due date. When you are reserving a newborn session before the due date, I can guarantee availability when the baby will born and we will schedule a session in the recommended period.
If a baby was born much earlier before the due date and spend time in NICU, a good time for a newborn session will be closer to the due date. If a baby came to the word later due date, the best time for the newborn session will be 14 days after the due date, because overdue babies are already coming older.