R.J.
The GCT is the SHORT version to test if you have gestational diabetes (which usually has no symptoms... just causes brain damage and heart defects in the fetus early pregnancy... and macrolitis (aka "fat baby", that usually cannot be delivered vaginally and has to be delivered via c-sect), and extremely low blood sugar after birth (just needs a few days or a week or so in the PICU... so you won't be taking them home for a bit, but no big deal... it only takes awhile to get their systems capable and it's pretty standard / low risk of infant death).
As far as yourself, there's SOME organ damage from all the sugar crystals in your blood, but only for a few months, so moms are usually fine / rarely have permenant damage. Diabetic comas and seizures can still happen, but those are rarely deadly.
So as far as pregnancy problems... GD is one of the better ones to have. Causes a c-section and about a week in the ICU.
The GCT short version weeds out about 90% of moms who are showing no signs of gestational diabetes (nearly all moms have SOME insulin resistance, pregnancy hormones really mess with us, but not at levels high enough to hurt us. Around 5% of women get gestational diabetes.. but about 15% test "probable" in the short version.
Only about 1/3 of women who test "proabable" in the short version actually have GD... but since they're probable for it... they all get the definitive test.
Which is about 5 hours long.
So, for me, a 1 hour test and a sugar crash is worth getting to avoid a 5 hour test with an even bigger sugar crash... but I'd do the 5 hour one if it made sure that we weren't looking at brain damage, heart defects, c-sect due to enlarged baby, PICU for baby's low blood sugar, and my own organ damage.
Just me.