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This conference explored two general areas: (1) the production and function of maternal hormones in pregnancy and (2) the production and function of fetal hormones and/or inductors. Progesterone late in pregnancy may be of maternal origin (ovarian) or of fetal origin (placental), depending upon the species under consideration. The identity of the "progesterone" or progestational steroid in the blood is still unknown. Whether "adrenal corticoids" are produced by the adrenals, maternal or fetal, or the placenta varies from species to species. ACTH may be produced by the placenta in some species but not in others. Stages of physiological evolution or adaptation are more evident than are basic generalizations.
Fetal inductor substances acting on adjacent tissues rather than through the general circulation require more explicit demonstration and definition as to their nature as "hormones," "morphogenetic agents,' or "differential catalysts." Surgical procedures on the fetus in utero have opened the field for
Bradbury JT. Gestation.. AMA Arch Intern Med. 1957;100(3):517. doi:10.1001/archinte.1957.00260090173026