My mother had this with my sister. I know it can be so bad that you have to watch your diet and even in some cases need an insulin shot daily. In my mothers case she just had to watch her diet (which she didn't really do effectively, and still managed to come out okay.)
From what I understand, it makes the baby REALLY huge. But other effects I am unsure of.
She will be put on a diet (not particularly a calorie-restricted diet, but one with a limited amount of sugar/carbohydrates) for the duration of the pregnancy. She will have her blood sugar checked fairly frequently, and if they are consistently abnormal while on the diet she may be given insulin and taught to monitor her sugars at home.
The goal is to regulate her blood sugars into a normal range in order to optimize the health of the baby and herself. Uncontrolled gest. diabetes can lead to an unusually large baby, or one that has problems with LOW blood sugar after birth.
Thank you. I was curious because I did not know anything about it.