Recurrent Hypoglycemia in Preemies Does Not Harm Development

Troy Brown

November 05, 2012

Recurrent hypoglycemia in premature infants does not appear to impair long-term development, according to a study published in the December issue of Pediatrics.

Win Tin, MD, FRCPCH, a consultant neonatologist from the Department of Neonatal Medicine at James Cook University Hospital in Middlesbrough, United Kingdom, and colleagues conducted the study because a previous study had found that premature babies with recurrent asymptomatic hypoglycemia (glucose concentration of ≤2.5 mmol/L [45 mg/dL]) experienced impaired motor and cognitive development at the age of 18 months. Results were similar when the children were seen again as part of another larger study at 7 or 8 years of age.

"These findings have profoundly influenced the neonatal care of the preterm infant across the developed world ever since, but while accepting that symptomatic hypoglycemia can cause lasting damage, many have doubted whether low levels are ever damaging when there are no associated clinical signs," Dr. Tin and colleagues write.

The researchers evaluated all children who were born in the north of England between 1990 and 1991 at less than 32 weeks' gestational age who had daily measurements of laboratory blood glucose levels for the first 10 days of life.

All of the index children and hypoglycemia-free children were matched for hospital that provided care, gestational age, and birth weight. They were assessed at age 2 years and again at age 15 years.

Of the 566 index children who lived to age 2 years, 47 had a blood glucose level of 2.5 mmol/L or less on 3 or more days.

The researchers observed no differences in developmental progress or physical disability in the children at age 2 years.

At the age of 15 years, 38 of the index children (81%) and the same number of control children agreed to undergo psychometric evaluation. IQ testing revealed almost identical scores (mean full-scale IQ, 80.7 vs 81.2).

Results were similar for an identical analysis of the 21 children who had a blood glucose level of 2.5 mmol/L or less on 4 or more days, 7 children who had a level of 2.5 mmol/L or less on 5 days, and 11 children who had a level lower than 2 on 3 different days.

In those children without sensorimotor disability, IQ measurement did not tend to be lower in children who had experienced hypoglycemia on numerous days.

"It would be unwise to assume that low blood glucose levels cannot be damaging in the preterm infant even in the absence of overt recognizable signs, simply because this study has failed to replicate the earlier study from Cambridge. All that the current study can do is show that the danger threshold must be lower than many had come to think it was," the authors write.

The authors have disclosed no relevant financial relationships.

Pediatrics. 2012;130.