Place of birth and whether they have the right to reside in HK.
When you register the babies birth, you will have been given a form ID235b which gives the baby right to reside in HK for the same amount of time as is remaining on the parents visa.
This is the form you take when converting it into a visa sticker that is put into you childs passport.
HK Immigration can check your child's eligibility from the airport. Takes two or three minutes.