Blood glucose concentration among premature babies

The importance of monitoring blood glucose concentration of premature babies in the hours and days following birth is highlighted by this recently published clinical study.

Although it is well established that prematurity is associated with increased risk of both hyperglycemia (increased blood glucose) and hypoglycemia (reduced blood glucose), prevalence data is sparse.

This study was designed to better define the prevalence and time course of hypoglycemia and hyperglycemia among premature neonates and identify possible associated risk factors.

Investigators enrolled a total of 141 babies born at gestational age < 34 weeks for study. This represented 90 % of all babies born at this degree of prematurity at their hospital during an 18-month study period.

Depending on their actual gestational age (GA) at birth, each of the 141 babies was assigned to one of four groups: GA < 28 weeks (n=21); GA 28-<30 weeks (n=15); GA 30 to <32 weeks (n=39); and GA 32 to 34 weeks (n=66).

Blood glucose was measured at least twice a day during the first 3 days of life and then at least once a day for days 4 through 7. On average, 17.5 blood glucose measurements per baby were made during these first 7 days of life.

For the purposes of this study, hypoglycemia was defined as blood glucose < 2.2 mmol/L (40 mg/dL) within 24 hours of birth and < 2.8 mmol/L (50 mg/dL) for the following days; and hyperglycemia was defined as blood glucose > 10.0 mmol/L (180 mg/dL).

By these standards, hypoglycemia occurred during the first week of life in 29 (21 %) babies and hyperglycemia occurred in 42 (30 %) babies.

Analysis of data relating time and blood glucose concentration revealed that median blood glucose of the whole study population was lowest (3.7 mmol/L) 1 hour after birth and highest (6.4 mmol/L) on day 7.

This reflects the finding that during the first two hours after birth, hypoglycemia occurred much more frequently (13 % of all babies) than hyperglycemia (1.4 % of all babies).

Hyperglycemia, which usually occurred during days 2 to 7, was found to be related to degree of prematurity; most frequently evident in the most premature group (GA < 28 weeks) and least frequent in the least premature group (GA 32-34 weeks).

However, this relationship between frequency of hyperglycemia and gestational age was found to be not statistically significant.

Likewise, no statistically significant relationship between hypoglycemia and degree of prematurity was evident. Risk factors identified for both hypo- and hyperglycemia were: being small for gestational age, low one minute Apgar score and failure to start feeding within 24 hours of birth.

The authors of this study conclude that blood glucose level monitoring is necessary in preterm infants, especially important for those who are small for gestational age and those with low Apgar score.

They maintain that early feeding (within 24 hours of birth) might be beneficial for maintaining normal blood glucose concentration during the first week of life.