The many pregnant women who have diabetes or develop it during pregnancy have another reason control their blood sugar: Abnormal glucose levels could affect their child’s memory, and damage might not be reversible.

A continuing study based at the University of Minnesota has tested children of diabetic mothers from day one through age 8 (and counting) and found consistent problems with their memory; specifically, their ability to recognize their mother’s voice (at birth), face (at 6 months), and sequences of actions (ages 3 and up). Researchers suspect that the impairment is caused by damage to the hippocampus, which rapidly develops during the third trimester of pregnancy.

“If the glucose levels in the mother fluctuate greatly … the fetus will also have high fluctuations in their glucose levels, which then leads to iron deficiency and oxygen deficiency” to the brain, says Tracy DeBoer of the University of California at Davis, one of the researchers. These deficiencies have been shown in animals to be especially damaging to hippocampus development, she says.

Much of our ability to remember the events we experience (called episodic memory) depends on the hippocampus, a small, metabolically active structure tucked deep into each hemisphere of the brain.

“Other research has shown that infants of diabetic mothers, when they do reach school age, have ‘poor cognitive outcomes,’ and that’s a very global term,” DeBoer says. “We’re really trying to be more neurally specific,” to pinpoint which aspects of memory might be affected.

A Battery of Tests

The study is part of a 20-year collaboration. Neonatologist Michael Georgieff at the University of Minnesota noticed that infants of diabetic mothers, who are often larger than average, often had lower stores of iron in their body than normal—and some had no reserve at all.

The researchers first studied sheep to discover what iron deficiency meant to the brain. “Ultimately, it sets up a competition for available iron coming from the mom” through the placenta, Georgieff says. Red blood cells win and get the iron they need, while the brain is deprived.