Obstetrics and Gynecology - A. M. Gromova 2000

Changes in the Woman's Body During Pregnancy
Metabolic Features Characteristic of Pregnancy

Biochemical changes associated with Pregnancy affect nearly every aspect of METABOLISM in the maternal Organism.

Energy Metabolism

Maintaining vital organ Functions under these new physiological conditions requires significantly more energy. Furthermore, the developing fetus is not yet self-sufficient in energy production and relies entirely on maternal metabolic resources to compensate for its needs. Consequently, the basal metabolic rate of a pregnant woman increases as gestation progresses. This is driven by elevated oxygen consumption and increased ATP utilization. The basal metabolic rate correlates directly with the combined body surface area of the mother and the fetus, which expands continuously throughout pregnancy.

As basal metabolism intensifies, energy carriers are rapidly generated and just as quickly consumed, necessitating an upregulation of protein, lipid, and, most importantly, Carbohydrate Metabolism.

Carbohydrate Metabolism

Glucose serves as the primary substrate for the fetus's energy demands. Meeting this increased demand requires a dynamic restructuring of the mechanisms regulating glycemic Homeostasis. As a result, levels of hyperglycemic Hormones—such as Glucagon, cortisol, estrogens, pituitary Growth Hormone and prolactin, along with placental lactogen—rise, leading to reduced glucose uptake by maternal Tissues, mobilization of hepatic Glycogen, and Gluconeogenesis from non-carbohydrate precursors. In response to this hyperglycemic stimulus, Insulin levels increase, particularly during the final month of pregnancy. The hypoglycemic effect of insulin stimulates appetite and food intake, while its anabolic properties promote Protein Synthesis AND the storage of glycogen and fat to build energy reserves.

A new dynamic equilibrium between hypo- and hyperglycemic mechanisms ensures an adequate supply of glucose to the fetus while maintaining normal Blood glucose levels in the mother.

Lipid Metabolism

During pregnancy, The rate of lipid metabolism increases. Plasma concentrations of Cholesterol and Fatty acids rise progressively, and their hepatic synthesis from glucose is activated, accompanied by lipid deposition in adipose tissue. The accumulation of fat stores in the maternal body continues until approximately 30 weeks of pregnancy, driven by high progesterone activity. After this point, fat accumulation in maternal tissues ceases, whereas lipid deposition in the fetus increases progressively. The latter stimulates the gonadotropic synthesis of estrogens, which enter the maternal Circulation to halt further lipid storage and enhance the transplacental transfer of Fatty Acids and glucose to the fetus.

Protein metabolism

During pregnancy, protein metabolism is regulated by the coordinated action of estrogens, progesterone, insulin, growth hormone, THYROID HORMONES, and placental lactogen. This orchestrated interplay enhances protein metabolism with a predominant shift toward anabolic processes.

Urinary nitrogen excretion decreases, particularly from the third trimester onward. Nitrogen required for the synthesis of fetal, placental, uterine, and mammary gland Proteins is retained in the maternal body, resulting in a positive nitrogen balance.

Driven by enhanced transplacental Amino Acid Transport to meet fetal demands, the utilization of proteins for uterine and mammary gland growth, and the accumulation of reserves necessary for postpartum Lactation, total plasma protein and its albumin fraction decrease in the pregnant woman.

Vitamin Metabolism

The activation of enzymatic systems increases the pregnant woman's physiological demand for Vitamins. Vitamin exchange between the fetus and the mother occurs across the placental barrier and relies on prior accumulation within the Placenta. If dietary intake is insufficient, the fetoplacental complex depletes maternal vitamin reserves to support the fetus, frequently resulting in maternal hypovitaminosis. Requirements for vitamins A, B, D, E, K, PP, and C increase two- to threefold. Vitamin C is essential for The Development of the fetus, fetal membranes, and placenta; vitamin A is required for fetal growth; vitamin B regulates The Nervous system; vitamin D ensures proper skeletal development; and vitamin E Supports the physiological progression of pregnancy.