An uncontrolled diabetic state during pregnancy results in serious medical complications to the fetus, occurring both in late gestation (ie hyaline membrane disease, hypoglycaemia) and in early gestation (ie abnormal organogenesis leading to malformations). Whether there are also deleterious effects of diabetes mellitus seen preconceptually, such as anovulation, or in early pregnancy, such as an increased rate of early fetal loss, is controversial. This report examines evidence that the diabetes may contribute to abnormalities in development beginning at these earlier stages of the developmental process.