Book excerpt: Type 1 diabetes is a serious and common disease, afflicting one per 200 of the population worldwide. It is widely believed to cause harmful physical maldevelopment--congenital malformations--and other consequences in the unborn children of women with the disease. This book considers the history of the disease in pregnant women and this belief that it causes anomalies since the time of the discovery of insulin in 1921, and presents a profound and critical appraisal of the subject of its supposed prenatal harmfulness.