High levels after giving birth
You should eat a normal diet following the birth of your baby. Some hospitals will advise to continue testing blood sugar levels after giving birth. Be prepared that you may see some high readings if you do this. It can take a while for your hormones to settle, hence the reasoning behind the recommendation of being properly tested for diabetes after at least 6 weeks.
So this suggests it can take up to 13 weeks or so to settle : )