A risk factor  is anything that increases a person's chance of developing cancer. Although risk factors often influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and talking about them with your doctor may help you make more informed lifestyle and health care choices.
The following factors may raise a woman's risk of developing a GTT:
Age. Being younger than 20 or older than 40 when becoming pregnant.
Previous molar pregnancy. A previous molar pregnancy may increase the risk of developing a GTT.
Nutrition/diet. Low levels of carotene and vitamin A in a person's diet may be associated with a higher risk of molar pregnancy.
Lower socioeconomic status. Lower socioeconomic status may be associated with GTT because of poor nutrition.
Blood type. The blood type of each parent may increase the risk of GTT. Specifically, the risk is increased if the woman has blood type A and the man has blood type O.