Hospitalization leave - when did you inform your boss?

Hi there, FTM here and currently week 35, EDD end July. I told my boss previously that I plan to start maternity leave around mid July. I asked Gynae abt hospitalization leave and he told me he’ll only grant this from week 37 onwards. Can anyone share how they communicate hospitalization leave to their boss? Do you tell them in advance that your gynae will start hospitalization leave in week xx? Thanks in advance!