Fig 7. Working model.

Under normal physiological circumstances, pituitary prolactin sustains CL function until mid-gestation, which is then taken over by placental lactogens. Decidual lactogens assist pituitary prolactin in pregnancy maintenance, while the latter plays the predominant role. Therefore, no obvious defects in fertility were noticed in Notch2 d/d mice. However, when the prolactin signaling is blocked, decidual lactogens were capable of ensuring progesterone production in Notch2 f/f mice, but Notch2 d/d mice experienced pregnancy loss due to insufficient level of decidual lactogens.