Is gestational diabetes caused by diet or some are at higher risk due to family history?

If your family has history of diabetes the risks are definitely much higher. I will say family history plays a big part because I have friends who eat veg healthily yet have gestational diabetes. With regards to diet , actually it is not just sweet stuffs which will cause diabetes. Very starchy foods like kway teow, rice or noddles will cause gestational diabetes too. If your family has diabetes history you may want to take note of your diet. Consuming more proteins rather than carbohydrates will be better