Neonatology Today

The normal healthy fetus receives a constant influx of glucose from the mother. This constant influx provides for basal fetal metabolism. The normal fetoplacental glucose utilization rate is 5 to 6 mg/kg/min. After 27 weeks gestation, this glucose influx also provides for convertion into glycogen, which is deposited mainly in the liver. The fetal glucose levels are maintained by transport of maternal glucose across the placenta along a concentration gradient by a facilitated, carrier-mediated diffusion1. Under normal circumstances, the source of fetal glucose is almost entirely derived from the maternal glucose pool1. There is a linear relationship between fetal and maternal glucose levels, with the fetal plasma glucose level being lower than that of the maternal plasma glucose. This linear relationship is maintained during maternal euglycemia, hypoglycemia or hyperglycemia1. In a normal healthy fetus, endogenous glucose production is either absent or very negligible. The enzymes for gluconeogenesis are present by the 2-3 months gestation and occurs from lactate, pyruvate or alanine2.