My diagnosis was PCOS, and we had leftover embryos for frozen transfer. I had a vaginal delivery. My RE was ok with me coming back and starting as early as 6 months; his only stipulation was that I should no longer be breastfeeding.
In the end, we waited nearly 2 years, because the sleep deprivation and PPA was intense.
I was told that, if I'd have had a c-section, their recommendation would have been to wait for a year and have a repeat HSG before doing another transfer.