[Plasma prolactin, progestrone and oestradiol during labour and postpartum (author's transl)]

The changes in the levels of plasma prolactin, progesterone and oestradiol were studied in 20 women during labour and immediately after delivery. The study of these levels shows that there is a mechanism for inhibiting the galactopoietic action of prolactin. Lifting this inhibition allows the milk to come in. This inhibition is probably due to circulating steroids, but this study does not allow us to differentiate clearly between the respective roles of oestradiol and progesterone, chiefly because of their short half-life.