Downgrading is definitely possible, from what I understand, even mid-way through or after delivery, you can switch to subsidised, and if baby needs NICU, the ward class can also be adjusted accordingly, so no need to stress too much about committing upfront. The main trade-off people usually weigh is that on the subsidised side, you won't have a dedicated gynae, so each visit or delivery you may see a different doctor, which some mums are fine with and others find unsettling. My friend delivered at KKH subsidised and said the care was actually solid, especially since if any complication arises, KKH tends to manage the billing on the subsidised side anyway, which keeps the costs from going very high. So it really comes down to whether continuity of care with one doctor matters a lot to you, if not, subsidised is quite a reasonable option and the switch process seems fairly straightforward to request.