The actual proclamation, passed three months before her birth, didn't specifically declare that the maternity ward itself was international territory. It simply stated that any place where Princess Juliana "may be confined" would, as long as she occupied it, be considered extraterritorial. No effort was made to define the exact size of the legal bubble of extraterritoriality surrounding her, just that it only applied to her and and any child she bore. So there's no presumption of it having any effect on others. You can see the proclamation (or at least a rather poorly-scanned version of it) at http://www.collectionscanada.gc.ca/databases/canada-gazette/093/001060-119.01-e.php?document_id_nbr=9450&image_id_nbr=340527&f=g&PHPSESSID=uiuuekdhfe657p57v0k666gb75