An increased risk for malignant neoplasm was found in children prenatally exposed to maternal type 2 diabetes, and the increased risk remained after excluding children with congenital malformations. An increased risk of disease of the circulatory system was found not only in children exposed to maternal diabetes but also in children exposed to paternal type 2 diabetes.
A higher prevalence of congenital malformations was found in children prenatally exposed to maternal diabetes, which is in line with previous studies. 
An increased risk of congenital malformation, however, was not seen in children prenatally exposed to paternal diabetes, which indicates that the observed association between maternal diabetes and congenital malformations may be due to the changes in intrauterine environment induced by maternal diabetes rather than genetic factors.
We found an increased risk of malignant neoplasm in children prenatally exposed to maternal type 2 diabetes and the associations seemed not to be modified by higher birth weight or preterm birth since the results did not change much when we adjusted for these factors. A previous study reported a higher rate of hospitalization due to neoplasms in children born to mothers with diabetes (OR
1.64, 95%CI: 1.06–2.54) 
but this was related to maternal insulin dependent diabetes. 
We did not see an increased risk of malignant neoplasm in children prenatally exposed to paternal diabetes. The results indicate that the risk of malignant neoplasm later in life may to some extent be programmed by a suboptimal intrauterine environment associated with maternal diabetes. The biological mechanism underlying the association is unknown but there are several possible factors that could play a role such as maternal and fetal hyperglycemia 
and the fetal response to these changes such as hyperinsulinmia. 
Medical treatments of diabetes during pregnancy may also play a role. Our findings are, however, based on few observations and larger studies with longer follow-up time are wanted. Congenital malformations did not act as a mediator for the observed associations between maternal diabetes and risk of malignant neoplasm since the results did not change much when we excluded children with congenital malformations from the analyses.
Intrauterine exposure to maternal diabetes is associated with childhood overweight, obesity, metabolic syndrome 
, and type 2 diabetes 
in the offspring, all of which are risk factors for diseases of the circulatory system. An increased risk of hypertension has been reported in offspring of diabetic mothers in humans 
and animals. 
We found an overall increased risk of diseases of the circulatory system, not only in children prenatally exposed to maternal diabetes, but also in children exposed to paternal type 2 diabetes, which suggest that genetic or other time-stable family factors also play a role. However, diseases of the circulatory system in our study population were, to large extent, related to congenital abnormalities rather than age-related cardiovascular diseases, which makes congenital malformations act as a mediator for the observed associations between maternal diabetes and risk of disease of the circulatory system. Longer follow-up time is needed for studies on atherosclerosis, myocardial infarction, stroke, and cardiovascular death. In addition, the endpoints in the current study were hospitalizations due to a category of diseases instead of hospitalizations due to a specific disease. Thus the observed associations between maternal or paternal diabetes and disease of the circulatory system may not apply to specific diseases in the categories.
Although type 1 diabetes and type 2 diabetes have common features in terms of increased level of glucose, triglycerides, and many amino acids in the maternal circulation, their genetic background and ability to modify the intrauterine environment probably differ. 
Previous studies suggest that changes in long-term health outcomes in the offspring of diabetic mothers are not strongly dependent on the type of maternal diabetes, 
which is supported by some but not all results in the current study.
We used a large population-based cohort including all children born in Denmark and had up to 30 years of almost complete follow-up. The completeness of the registration of diabetes, malignant neoplasm, and diseases of the circulatory system is high since health services, including antenatal care and hospitalizations, are free of charge for all citizens in Denmark. However, some women have type 2 diabetes without knowing it 
and their children will remain in the unexposed cohort, which would attenuate the associations slightly. In addition, some misclassification between different types of diabetes is likely, 
especially between 1987 and 1993. We were able to adjust for a number of variables in the analyses but unfortunately, we had no data on lifestyle factors such as maternal smoking, pre-pregnancy body mass index, or breast-feeding. The observed associations could be confounded by these factors.
This study suggests that susceptibility to malignant neoplasm and congenital malformation may be results of fetal programming induced by maternal diabetes. The risk of disease of circulatory system may be related to genetic factors or other time stable family factors as well as fetal programming. Congenital malformation may act as one of the potential pathways of associations between diabetic intrauterine environment and risk of diseases of the circulatory system in children prenatally exposed to maternal diabetes. We had insufficient follow time to examine risk of atherosclerosis and other aging related cardiovascular diseases. Paternal diabetes had no association with congenital malformation measured as prevalence at birth.