Can galactulose and fructose affect gestational diabetes?

Not as much: Both fructose and galactose are of low glycemic index and are not regulated by insulin. They are slower absorbed than glucose and therefore don't cause blood glucose to rise. Excessive use of fructose, however, can lead to increase in central fat deposition and metabolic syndrome that can lead to significant cholesterolemia and atherosclerosis.

Yes: Both are forms of sugars.