Abstract
FROM the moment of conception an interplay of biochemical processes ensures the growth and development of the fetus and its placenta. Such an interplay must function under an intricate system of controls of which we have only limited knowledge. The efforts of many investigators have accumulated a wealth of data relating to steroid metabolism that have suggested a collaborative enterprise between fetus and placenta. These data are examined in the special context of a "fetoplacental unit," and an attempt is made to place the steroid story in perspective along with other aspects of fetal and placental endocrinology.† For the reader . . .