Concentrations of estrone (E1), estradiol (E2), progesterone (P4), and cortisol (CRT), and 4β-hydroxycholesterol (4β-OH-CHO) and the 4β-OH-CHO:CHO ratio (endogenous biomarkers of CYP3A activity), were quantified in human plasma across a spectrum of pregnancy states: healthy nonpregnant controls (n = 4), healthy pregnant volunteers (n = 6), and pregnant patients diagnosed with preeclampsia (n = 8). The gene discussed is CYP3A4; the disease is preeclampsia.