Deciding when to ttc #2

My husband and I decided shortly after we got married that we want 2 kids and want them fairly close together.

Our plan was to start trying for #2 when the first baby is 18-24 months.

Part of me wants to start trying right away at 18 months postpartum because (if we do get pregnant right away) baby will be due in February and I’d love to have an end of winter baby and I feel like April-February would be a good time to be pregnant. We got pregnant the first try with our first and were both told we’re very fertile. However, I had gestational diabetes in my first pregnancy and was told that I basically have a 60% chance of having it again the second pregnancy and it will most likely be worse the second time. If we followed this timeline, I’d have gestational diabetes during Christmas!

I know it’s only a short period of time to have gestational diabetes, but it made me very depressed last pregnancy.

As far as age gaps, would anyone recommend starting to try right at 18 months, or wait until she’s 2?

Thanks!