Scheduled c section

This is my first time scheduling a csection and was wondering how long they wait to schedule one. I’m only 15w so obviously it won’t be brought up for awhile but was wondering when doctors started discussing it with you guys. My OB and I have already discussed having another csection so I know it’s on my file. Also, do you choose the day or do they just schedule for a day that they know they’ll be free to do the surgery? I’m also wondering since I have diabetes (Type 2) and high BP if they’ll schedule me at 38 weeks or earlier. Any input is appreciated!