PBS dependant application form

Hi, i have tier 2 general visa and i want to apply visa for my new born son as a dependant. i was wondering that lots of sections on the PBS dependant visa application form are not applicable to the newborn dependant applicant but they are i think mandatory to fill in !! so what should i do? should i leave these sections blank? also newborn passport is not available at the moment but i will get it sometime in November. Someone told me that for newborn visa application i only need his birth certificate and not the passport. is it true?
please let me know.thanks Syed