Little is known about the causes of childhood cancer, partly as not many children develop cancer, although childhood cancer is a leading cause of death by disease in the young. The young age of the children suggests that risk factors for childhood cancer may be present during pregnancy. Previous studies have shown that exposure to trans-fat, a type of unsaturated fat common in industrially produced foods (iTFA), has adverse health effects in adults, including the risk of developing cancer. Haematopoietic neoplasms are the most common cancer types among European children under the age of 15 years. This study will bring new knowledge as to whether trans-fat and other fatty acids may also increase the risk of developing haematopoietic neoplasms during childhood.