Oral glucose tolerance tests in newborn infants

Oral glucose tolerance tests ( GTTs ) were performed on 15 fullterm (Group I), 12 preterm low birth weight (Group II) and 16 preterm very low birth weight (Group III) infants who were clinically stable. GTT was done on the third postnatal day in Groups I & II and serially at different postnatal ages in Group III (days 3, 7, 14, 21 & 28). After 4 hours of fasting capillary blood samples were collected for plasma glucose estimation at fasting and for a 3-hour period following oral intake of 1.75 gm/kg of glucose. Mean plasma glucose levels were comparable in Groups I & II at all stages. Group III infants had lower mean plasma glucose which increased with postnatal age. Significantly higher values were observed as late as 150 minutes in days 3, 7 & 14 groups compared with days 21 and 28 of Group III. Our data suggest that larger and more mature preterm low birth weight infants (greater than or equal to 1501 gm and greater than or equal to 34 weeks' gestation) were capable of handling glucose as efficiently as term infants. Preterm very low birth weight infants (less than or equal to 1500 gm and less than or equal to 33 weeks' gestation) exhibited impaired glucose tolerance during the first two weeks of life.