Australasian Science: Australia's authority on science since 1938

Low Blood Sugar in Newborns Linked to Later Difficulties

A newborn condition affecting one in six babies has been linked to impairment in some high-level brain functions that show up by a child’s fifth birthday.

An international research team following 614 New Zealand babies born at risk of low blood sugar levels found that children who had experienced the condition were up to three times more likely to have difficulties with executive function (skills for problem-solving, planning, memory and attention) and visual-motor co-ordination (skills for fine control of movement, and understanding what you see) at age 4.5 years than children who had normal blood sugar levels.

Overall, the lower the blood sugar levels, or the more often they dropped, the greater the impairment was. Children who had experienced a drop in blood sugar that was not detected using routine blood sugar monitoring were four times more likely to have difficulties with these skills. There was no link with lowered intelligence as measured by IQ.

The findings were published in JAMA Pediatrics.

Low blood sugar affects up to 15% of all babies, and is the only common preventable cause of brain damage in infancy. At-risk babies – up to one-third of all born – are those born premature, smaller or larger than usual, and babies whose mothers have diabetes.

Health guidelines say at-risk babies should be tested with heel-prick blood tests in the first few hours after birth. If their blood sugar is too low they are treated with a dextrose gel to return it to normal levels – a breakthrough treatment pioneered in 2013 by study leader Prof Jane Harding of The University of Auckland’s Liggins Institute.

“At 2 years there was no relationship between blood sugar levels and later brain development, but at age 4.5 years it’s clear that the children who experienced low blood sugar levels were more likely to have specific difficulties,” Harding said. “We don’t know yet what these impairments mean for the child in practical terms, but executive function and visual motor integration are believed to be important for learning at school, particularly for maths and reading.”

To investigate whether the impairments at 4.5 years translate to learning or behaviour difficulties at school, the research team are now starting to follow the children at age 9–10 years.

“What was especially concerning in our 4.5-year results was the fourfold increase in risk of executive function difficulties in children who had experienced low blood sugars that were not detected in routine testing,” says the paper’s lead author, Dr Chris McKinlay of the Liggins Institute. “This is the first time this has been shown.”

Internationally there is no agreed cut-off for safe versus unsafe levels of blood sugar in newborns, McKinlay says. “If we find at age 9–10 these children are more likely to have reading and maths difficulties, then we may urgently need to rethink what the diagnostic threshold should be,” Harding adds. “And if even children who were treated are at greater risk of impairment, this raises the possibility that some damage is already done before they receive treatment.”

This makes the findings of another study Harding is leading, hPOD, all the more relevant. “In hPOD, we’re looking at whether the dextrose gel treatment could be routinely given to all at-risk babies as a preventative, before they develop low blood sugars – and before any damage could be done,” she said.