Fetal growth curves: does classification of weight-for-gestational age predict risk of hypoglycemia in the term newborn?

Our objective was to determine whether classification of birth weight as small, average, or large for gestational age using published fetal growth curves is predictive of a term infant's risk of hypoglycemia. This prospective, descriptive study measured and plotted birth weight measurements on six published fetal growth curves to classify infant birth weight as small, average, or large for gestational age. Glucose levels were measured 2 hours after birth to determine the prevalence of hypoglycemia. The sensitivity, specificity, and positive/negative predictive values were calculated for each fetal growth curve, and odds ratios were calculated. The patients were 157 clinically stable term Caucasian and African American infants of nondiabetic mothers from a community hospital in midwestern United States. Ten of the 20 (50%) infants with hypoglycemia were classified as average for gestational age on all six published fetal growth curves. Calculated odds ratios demonstrated that none of the six published fetal growth curves significantly predicted the risk of hypoglycemia based on classification of birth weight as small, average, or large for gestational age. The risk of hypoglycemia in term infants was not accurately predicted by classification of birth weight as small, average, or large for gestational age. Clinicians should use other methods to predict which term infants are at risk for hypoglycemia.