CYP3A4 and preeclampsia: Here, we studied the association between maternal plasma concentrations of key steroidal PRHs (E1, E2, P4, and CRT) and endogenous 4β-OH-CHO biomarkers of CYP3A activity (4β-OH-CHO concentration, 4β-OH-CHO:CHO ratio) across a spectrum of pregnancy states (nonpregnant, healthy pregnant, pregnant diagnosed with preeclampsia) in humans, and the impact of PRHs on CYP3A4 protein expression in SCHH.