For the style of newborn photography that you see in my portfolio, newborns need to be under 2 weeks old, as they hit a growth spurt at around 14 days old and become fussy and developmentally very different from when they first arrived.
Leo here, is almost one month old! This age is very tricky to photograph, as they are going through growth spurts, and are uncurled, alert, and fussy when not feeding. Luckily, he closed his eyes long enough to get some peaceful sleeping portraits!