Is gestational diabetes hereditary?

Yes, but partially: Gestational diabetes, which is often a precursor to type 2 diabetes, has a strong hereditary genetic component. The tendency for the body to be insulin-resistant and insulin-deficient (leading to high sugars) are often transmitted in the genetic make-up. However, gestational diabetes is also strongly related to other non-hereditary factors like age, weight, physical activity levels, and diet habits.

Not really: Not really, but is kind of one of those "runs in the family" type problems.