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). Here, CLOCK is linked to preeclampsia.