GLOW Babies Study: Understanding normal glucose levels in healthy babies in the first days after birth

A landmark study led by a Te Herenga Waka—Victoria University of Wellington researcher has determined accurately, for the first time, what normal blood glucose levels are in healthy newborn babies in the first days after birth.

Blood glucose levels fluctuate following birth, and a screening test (commonly known as the heel prick blood test) is offered in New Zealand for babies who are considered at-risk of hypoglycaemia, to determine whether glucose levels are too low.

At-risk babies are those who are born preterm, small, or large for gestational age, infants of diabetic mothers, or those not feeding well. Babies with low blood glucose levels need to be treated promptly as low levels are linked with poor neurosensory outcomes in children. However, what is considered normal when it comes to blood glucose levels has, until now, remained unclear.

The Glucose in Well Babies (GLOW) study, led by Dr Deborah Harris, found that many healthy babies reach glucose levels below the level at which they would normally be treated for hypoglycaemia if they were considered at-risk. Importantly, the findings also found that in healthy babies it can take up to four days for glucose levels to return to normal following birth.

Dr Harris says this is a considerable step forward in global understanding about what is normal in the first days of life.

“Our findings can’t be extrapolated to conclusions about the management of babies at-risk of low blood glucose levels, but they do form the foundation for a discussion around what is abnormal, and how long and when blood glucose screening is required for at-risk babies to ensure adequate treatment.”

The question of exactly when low blood glucose levels could indicate a more serious disorder has long been controversial and this gap in knowledge has resulted in differences in clinical guidelines from neonatology and pediatric organisations in terms of when and how to treat low blood glucose, and when the possibility of more serious conditions can be ruled out in at-risk babies.

Dr Harris says that this new knowledge will help bridge the gap and will also provide a foundation for future research in this area, with her research team looking to explore when and how screening should happen in future research.

“We have known for a while how to treat at-risk babies who have glucose concentrations below what we think is safe but describing what is normal has until now has been a missing part of this puzzle,” she says.

“Clinicians have been largely in the dark regarding glucose level patterns in babies who are considered healthy, and we were able to shed some light through this study of a unique cohort of healthy babies who were largely at home during the study, rather than in hospital.”

The GLOW Babies study was conducted through the Newborn Intensive Care Unit, Waikato District Health Board, Hamilton, New Zealand.