Hello and welcome to HCM,
Is there any history of
jaundice at birth?
Since, your child is 3 weeks pre-mature there is a possibility that the
bilirubin levels could have been raised.
The raised bilirubin can cause the skin to look dark.
The skin can darken after exposure to sunlight.
This
tanning goes off slowly over a period of time.
The body and facial hair in a baby are called lanugo and they are shed off at the time of birth.
You can try ways to avoid darkening of skin.
Cover bare parts of the body when the baby is kept in sun.
The facial features and other parameters change as the baby grows.
There is no set time when the features or complexion becomes permanent.
This depends on genetic,intrinsic, and extrinsic factors.
Thanks and take care
Dr Shailja P Wahal