SAN FRANCISCO, CALIFORNIA--Diabetes is a common problem during pregnancy, affecting roughly 10% of expecting mothers. New research presented here yesterday gives these moms-to-be extra reason to keep their blood sugar under control: Not doing so may impair the development of a baby's hippocampus and cause subtle but lasting memory deficits.
Previous studies have found that children born to diabetic mothers tend to score lower than their peers on general cognitive tests, says Tracy DeBoer, a psychologist at the University of California (UC), Davis. But the specific nature of the deficit isn't clear, she says, nor is the mechanism. Based on research with rodents, DeBoer suspected that low iron levels might be part of the problem. When pregnant rats are diabetic, the fetus develops an iron shortage in the brain that dampens metabolic activity in neurons, particularly in the hippocampus, an important memory center.
DeBoer investigated this potential link between iron and memory in 40 human infants. She sampled umbilical cord blood drawn at birth to measure levels of an iron-binding protein called ferritin, an indicator of iron levels. Then, when the infants were 12 months old, she tested their memories.
(The memory test DeBoer used works like this: A researcher first demonstrates a simple action, such as putting a toy car in a container and a short time later, shows the infant images related to what they'd seen. Given a choice, infants will look longer at a novel image than something familiar, so if they remembered seeing the car go in the container, for example, they should look longer at an image of something else than they would at an image of the car.)
At 12 months, infants who had had low ferritin (and presumably low iron) levels at birth did worse on the memory test, DeBoer reported in a paper published in Developmental Medicine & Child Neurology in 2005. When DeBoer caught up with the same children between the ages of 3 and 4 years, the memory deficits had persisted in those born with low iron levels. In addition, recordings from scalp electrodes taken while the toddlers took the memory test suggested abnormalities in memory-related brain activity in the low-iron group, DeBoer reported here yesterday at the meeting of the American Association for the Advancement of Science (which publishes ScienceNOW). DeBoer points out that not all of the infants born to diabetic mothers had memory deficits--only the ones born with low iron.
"The work has clear implications for raising healthy babies," says Lisa Oakes, a psychologist at UC Davis who studies infant memory but does not collaborate with DeBoer. "It underscores the importance of controlling diabetes during pregnancy, and it provides us a place to look when evaluating and developing interventions for children who may have experienced this type of insult prenatally."