While the signals that initiate parturition in humans and other Catarrhine primates are unknown, it has been proposed that a ‘decidual clock’ may regulate the successful establishment and maintenance of pregnancy, such that severe decidualization defects lead to infertility, moderate defects lead to recurrent pregnancy loss/recurrent spontaneous abortion, and mild defects lead to preterm birth (Norwitz et al., 2015). Here, CLOCK is linked to Infertility.