Previous studies have found DNA methylation changes in circadian clock and clock-controlled genes in the placenta and neonatal tissues of early-onset and late-onset preeclampsia (EOPE and LOPE), and consistent with our findings, differential DNA methylation of the CLOCK gene was observed in umbilical cord leukocytes (UCL) of EOPE compared to uncomplicated controls [40]. This evidence concerns the gene CLOCK and preeclampsia.