Clinical biochemistry of pregnancy.

Major adaptations in maternal physiology and metabolism are required for successful pregnancy outcome. Hormonal changes initiated even before conception significantly alter maternal biochemistry early in pregnancy. Steroid hormones, peptide hormones, and prostaglandins interact to expand blood and plasma volume and modulate the maternal capacity to supply energy and nutrients to the fetoplacental unit. As gestation progresses, reference ranges for the concentration of many biochemical parameters change significantly from those found in the nonpregnant state. Gestation-specific reference ranges are essential for correct interpretation of tests used in screening, diagnosis, and monitoring during pregnancy. The use of clinical laboratory tests in the management of high-risk pregnancy are discussed from the perspective of testing before conception and during pregnancy.