Stillbirth & gestational diabetes correlation?

Apple
Just found out we're pregnant and due March 2017. I don't have diabetes and am not pre-diabetic either. However I am 200lbs+. A family member had gestational diabetes and sadly had a still born a week before her scheduled c-section. There's a lot of family pressure to not gain weight and talk of how her weight (300+) and diabetes caused the stillbirth. 
Has anyone been told this by their doctor? Has anyone experienced loss that doctors thought correlated with weight and diabetes? Please help. Terribly worried 😰😰