Low blood sugar at birth increases risk of impairment in some brain functions

Low blood sugar levels in new-borns doubles or triples the chance of impairment in some brain functions later in life, a new report has found.

Research published in today's issue of JAMA Pediatrics found that children who had low blood sugar levels as new-borns were two 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 the age of four-and-a-half.

Low blood sugar is a condition which affects about 15 per cent of new-borns and is the only common preventable cause of brain damage in infancy. At-risk babies are those born premature, smaller or larger than usual and babies whose mothers have diabetes.

The study, Children with Hypoglycaemia and their Later Development, was carried out by a team of researchers from the Liggins Institute, the University of Auckland, Waikato Hospital, the University of Canterbury and the University of Waterloo and found 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.

The team, led by Distinguished Professor Jane Harding at the University of Auckland-based Liggins Institute, have been following 614 New Zealand babies born at risk of low blood sugar levels to see what the effect was.

At-risk babies are tested with heel-prick blood tests in the first few hours after birth. If their blood sugar is too low, they are treated with sugar gel to return it to normal levels.

Half of the babies in the study were diagnosed with, and treated for, low blood sugar within hours of birth.

The children were assessed at two years old and again at four-and-a-half.

"At two 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."

The research team will next assess the children at the age of nine or 10 and the findings could make the results of another study she is leading even more important.

The other project is looking at whether sugar gel should be routinely given to all at-risk babies as a preventative.

A mum's relief

The study results have confirmed for one mum just how lucky she is.

While pregnant with her second eldest son, Kawiti, mother-of-four Arihia Nordstrom was identified as high-risk because she had Type 1 diabetes.

When Kawiti, now 8, was born, his blood sugar plummeted. He was so pale and lethargic doctors knew his blood sugar was low without testing him and immediately gave him sugar gel.

In his first two days of life his sugar levels dropped another three times but the testing carried out when he was four-and-a-half found nothing wrong.

The Northland mother's eldest son, who was born premature, and her third child were also born with low sugar levels but, based on their development, Nordstrom believed they too had escaped without suffering any effects.

"I was lucky," she said.

But the findings would be an important tool for other parents because they could be given information about what signs to look for and how best to help their child overcome any difficulties, she said.

Given the high number of children born with low blood sugar, Nordstrom believed all new-borns should be checked as a matter of routine.