Low Blood Sugar a Marker for Babies at Neurological Risk During Delivery, NewYork-Presbyterian/Weill Cornell Study Suggests

Testing for Hypoglycemia Might Help Save Newborns from Brain Damage, Alerting Doctors to the Danger Early On

Sep 23, 2004


Abnormally low blood sugar may raise an infant's risk for brain damage during delivery, according to a new study led by a NewYork-Presbyterian Hospital/Weill Cornell Medical Center researcher. He believes early testing for neonatal hypoglycemia might potentially reduce neurologic morbidity.

"In full-term babies already at elevated risk for brain damage, low blood sugar increased that risk 18-fold," said Dr. Jeffrey M. Perlman, Professor of Pediatrics at Weill Cornell Medical College, and Chief of the Division of Newborn Medicine at New York-Presbyterian/Weill Cornell.

His team's study is published in the journal Pediatrics.

About 1 in every 1,000 deliveries in the U.S. ends with the newborn suffering severe, often irreversible brain damage due to a lack of oxygenated blood flow to the brain.

"Such babies can die, and if they survive, the long-term effects can be devastating," Dr. Perlman said. "Usually it's severe forms of cerebral palsy."

Unfortunately, obstetricians are still looking for a reliable method of spotting these problem deliveries early on, when interventions might help prevent or limit neurological damage.

Already, one factor — fetal acidemia, or a high blood acidity in the umbilicus, related to interrupted blood flow — has been shown to be a "red flag" for subsequent brain injury.

Dr. Perlman theorized that low levels of glucose in umbilical cord blood might be another such marker. The reasoning is simple: "All of us, babies included, need glucose as an energy source in the brain. If your blood sugar is low, then your brain has a reduced energy source. It's running on — or near — empty."

In their retrospective study, Dr. Perlman and colleagues compared the blood sugar levels and neurological outcomes of 185 full-term infants with severe fetal acidemia, admitted to the neonatal intensive care unit at the University of Southwestern Medical Center, Dallas, where Dr. Perlman conducted much of the research before joining Weill Cornell.

Overall, 41 of the infants developed some form of brain damage, including 14 who died due to severe neonatal encephalopathy.

"What we found was that 27 of the 185 babies in the study had a blood sugar level at delivery of 40 milligrams per deciliter or below — a level we believe could raise risks for brain damage," Dr. Perlman said. "And, indeed, among these 27 babies, 15 went on to suffer some level of neurological injury — 56 percent."

In contrast, just 16% of the 158 babies with blood sugar over 40 mg/dL went on to develop brain damage.

Dr. Perlman stressed that, on its own, initial blood sugar at or below 40 mg/dL may not pose significant risk. However, hypoglycemic neonates do seem more vulnerable to brain damage, especially those with severe fetal acidemia who also require resuscitation during delivery. Overall, that combination of factors raised risks for neurological damage 18-fold, the researchers found.

"This is a retrospective study," Dr. Perlman cautioned, "so more needs to be done to determine whether it's simply that the sickest babies were more likely to have low blood sugar, or whether, if you treated the glucose deficiency early on after birth, you might be able to reduce subsequent brain injury."

"But the findings suggest that, in the context of other factors, we may need to measure blood sugar earlier rather than later," he added. "The 'Holy Grail' of all this research is to develop what we call neuroprotective strategies — to intervene quickly when we believe a neonate is at especially high risk, limiting the damage."

Co-researchers on the study include Dr. Walid A. Salhab, Dr. Myra H. Wyckoff, and Dr. Abbot R. Laptook — all of the University of Texas Southwestern Medical Center, in Dallas.

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