At this stage, when the primary placenta begins to form35 and Pibf1 is deleted in all cell lineages of the labyrinthine interhaemal membrane (Fig. 3a), the loss of Pibf1 led to defective placentation and embryogenesis (growth restriction in size, failed tail turning, pericardial effusion) (Fig. 3b). The gene discussed is PIBF1; the disease is pericardial effusion.