Maternal-fetal metabolism in normal pregnancy and preeclampsia

Adaptation to pregnancy in humans involves major anatomic, physiologic and metabolic changes in the mother in order to support and provide for the nutritional and metabolic needs of the growing conceptus. Metabolically, pregnancy is marked by several important and dynamic adjustments including increased insulin resistance, hyperlipidemia and changes in protein and amino acid metabolism. In general, these metabolic adaptations serve to increase nutrient availability for the benefit of the growing fetal-placental unit. Interestingly, the pregnancy complication preeclampsia is recognized to evidence biologic exaggerations of these normal metabolic adaptations of pregnancy. Specifically, preeclampsia is associated with increased insulin resistance, hypertriglyceridemia, high circulating free fatty acids, low high-density lipoprotein particles, and high maternal and fetal plasma amino acid concentrations. These metabolic alterations may contribute to the pathophysiology of the syndrome and may also influence fetal growth. The focus of this review will be to summarize the normal metabolic adaptations, transport and utilization of carbohydrates, lipids and amino acids that occur during pregnancy. Furthermore, we will review the differences in carbohydrate, lipid and amino acid metabolism in pregnancies complicated by preeclampsia in comparison to uncomplicated pregnancies.