Perinatal risk factors increase the risk of being affected by both type 1 diabetes and coeliac disease.

Aim: This study investigated whether perinatal factors influenced the risk of a double diagnosis of type 1 diabetes and coeliac disease.

Methods: We used multinomial logistic regression models to study the associations between perinatal factors, gender, mode of delivery, season of birth and the risk of type 1 diabetes, coeliac disease or both, in Swedish-born singleton children.

Results: We found that 4327 of the 768 395 children (0.