For pregnant women with type 1 diabetes, good control of blood sugar might make a difference in how well their child does in school years later, according to new research from Denmark.

Overall, children born to mothers with type 1 diabetes achieved similar grades in primary school when compared to other children, the study found, but for the children of diabetic mothers, academic achievement was “quite divergent” depending on how well mothers had controlled their blood sugar before and during pregnancy.

The study authors caution in the journal Diabetes Care that it’s not clear if exposure to high blood sugar levels during pregnancy affected children’s brains directly, or family factors that affected mothers’ ability to control their blood sugar also influenced children’s cognitive development.

“Good diabetes control prior to and during pregnancy is important in other ways, as it lowers the risk of birth defects, preeclampsia, preterm delivery, large birthweight babies, and low blood sugar in the newborn,” said Dr. Florence Brown, director of the Joslin Diabetes Center - Beth Israel Deaconess Diabetes and Pregnancy Program in Boston, who was not involved in the study.

“But when we see an association between maternal higher (blood sugar) in pregnancy and worse offspring academic achievement we cannot say that there is cause and effect,” Brown said in an email. “While the authors try to adjust for the effect of parental education on child educational performance, there may be other factors that influence offspring academic achievement.”

The study authors, led by Dr. Sine Knorr at Aarhus University Hospital, looked at medical records to track blood sugar levels pre-pregnancy and during pregnancy for women with type 1 diabetes, and used school records to follow the performance of 707 of their primary-school-age children.

They also compared those children to more than 60,000 similar school children whose mothers did not have diabetes.

Children born to women with good control of their blood sugar tended to have better than average grades as compared to their peers in the general population. This was particularly true for the children of women who maintained good blood sugar control during their third trimester of pregnancy.

But the reverse was also true. When mothers had poor control of their diabetes before and during their pregnancy, their children had lower grades. The poorer the control, the worse children did in school, when they were compared to the offspring of women without diabetes.

The study team also found that there was a strong relationship between the mother’s level of education and her blood sugar control. The more educated women were, the better they seemed to be at controlling their diabetes.

There was also a strong association between parental education and their children’s school grades, but even after the authors took that into account, the relationship between blood sugar control in pregnancy and kids’ school grades persisted.

Brown pointed out that a mother’s social, psychological and cognitive function beyond her educational attainment would be expected both to improve her diabetes control and enrich the learning environment of her child.

“This is supported by the fact that women with the best diabetes control . . . in pregnancy had offspring that performed better academically than offspring of . . . women without diabetes,” she said. “The authors of this study do endorse this as a possible explanation for their findings.”

These results only pertain to type 1 diabetes, the less common form of the disease that typically begins in childhood and must be controlled with administered insulin, researchers caution. Type 2 diabetes, most frequently diagnosed in middle adulthood, is much more common, and has different underlying causes. In addition, gestational diabetes is a separate condition that occurs during pregnancy and usually disappears after the baby is born.

“I don't know of any study of this type that was done with women who had gestational or type 2 diabetes,” said Dr. Jorge H Mestman, director of the University of Southern California Center for Diabetes and Metabolic Disease in Los Angeles. “So we can’t apply these results to other types of diabetes.”

Overall, the study is very provocative and the results are exciting, Mestman noted, “but it needs to be repeated.”

Mothers with very poor blood sugar control may have had other complications, and that would need to be accounted for, he added.