If you need your pictures for a special purpose I recommend to book at least 4 to 6 month in advance.  If you would like to have a maternity photoshooting than the best time for you to have your photoshooting is 6 to 10 weeks before your due date. Then your belly looks the best. If you don’t have a special occasion than you should book minimum 2 weeks in advance to have time for planning your shoot.