Is your boss an American? Many Americans appreciate privacy more than anything. Unless you and your boss are also friends and she has explicitly expressed that she does not mind people’s visit during her maternity leave, it is not necessary to go visit her.

My boss just had her 1^st baby a few months ago. She and I have had a close working relationship and I consider her as my mentor and a friend. So I kept in touch with her during her leave – called her a few times and also sent her a flower basket right after she gave birth to her baby. I never suggested going visit her though.