Decline in the concentration of low-density lipoprotein-cholesterol in human fetal plasma near term

Fetal plasma levels of lipoprotein-cholesterol were quantified during the latter stages of normal human gestation to ascertain whether a relationship exists between fetal adrenal steroid production and the concentration of plasma lipoprotein-cholesterol. It was found that total cholesterol and low-density lipoprotein (LDL)-cholesterol levels in fetal plasma declined progressively from 33 to 42 weeks of gestation. At 41 to 42 weeks of gestation, the fetal plasma concentrations of total cholesterol (53 ± 3 mg/dL, mean ± SEM) and of LDL-cholesterol (28 ± 2 mg/dL) were significantly lower (P < 0.001) than those at 33 to 34 weeks of gestation (73 ± 7 mg/dL and 49 ± 6 mg/dL, respectively). However, there were no fluctuations in the plasma concentrations of high-density lipoprotein (HDL)-cholesterol during this period of fetal development. The fetal plasma levels of dehydroepiandrosterone sulfate (DS), the major secretory product of the fetal adrenals, rose significantly between 33 and 42 weeks of gestation. Since LDL-cholesterol is utilized as substrate for fetal adrenal steroidogenesis, it is suggested that the increasing rate of growth and steroid production by the fetal adrenals near term is causally related to the significant decline in the concentration of both LDL-cholesterol and total cholesterol in fetal plasma during normal human development.