We aim to develop three different placental epigenetic clocks: 1) a “robust placental clock” (RPC) that is largely unaffected by pregnancy conditions (e.g., preeclampsia, gestational diabetes, and trisomy), 2) a “control placental clock” (CPC), tailor-made for measuring GA in normal pregnancies, and 3) a “refined RPC”, trained for uncomplicated term (GA>36) pregnancies. Here, CLOCK is linked to preeclampsia.