PER3 and preeclampsia: Our recent studies in human placenta indicate that co-alterations of the molecular clock mRNAs NR1D2, CLOCK and PER3 are significantly associated with term preeclampsia (Zhou et al., 2022), whereas co-alteration of CLOCK and CRY2 at the mRNA levels in second trimester maternal blood are significantly associated with an increased risk of sPTB (Zhou et al., 2021a).