I think this is probably a conversation you need to have with your medical team, as they know your medical history and whether you are more at risk if you delay your next pregnancy.
However, the other way to look at it is what would you do if you weren't diabetic? Diabetic pregnancies are pretty well managed these days.
Another factor which isn't diabetic dependent and which may or may not be relevant is what sort of maternity leave entitlements you'll have if you start with a new job and then try to get pregnant in a year's time.
(And for what it's worth (not very much) my children are now in their twenties and I had them at 29 and 33 - the second pregnancy was easier because I managed it slightly better.)