When the sugar test results are reported high and the pregnant woman comes to the diabetes clinic, frequently the first thing she says is “I failed the test”. I don’t think this is fair. You did not fail the test, your pancreas did so please do not dump on yourself, if you have to pick on anyone, pick on your parents who gave you a pancreas that was not up to the stress of pregnancy.
Gestational diabetes is due to a combination of not enough insulin and the insulin resistance of pregnancy. In pregnancy the hormones from the placenta or afterbirth block how insulin works and this allows the blood sugar to rise, simplistically we think of it as a way to provide more energy to the baby. The mom’s pancreas has to make more insulin to keep this in check and if it does not then the sugar will rise too high and we have gestational diabetes. It is true that excess weight present either before the pregnancy or gained during the pregnancy will make the insulin resistance worse and so increase the workload on the pancreas Thus the mother’s weight contributes to the situation but the big determinant of whether someone will have gestational diabetes is how well the pancreas works, something that is more under genetic control.
If gestational diabetes is diagnosed it is better to use the time as an opportunity to get things right for the baby and for your self in the long term. When life gives you a lemon, make lemonade.