Abstract
The placenta is essential to mammalian pregnancy with many roles beyond just nutrient supply, including both endocrine and immune functions. During the course of evolution, the placenta of higher primates has acquired some unique features, including the capacity to secrete corticotropin-releasing hormone (CRH). In addition, a placental receptor for IgG enables particularly high levels of protective maternal antibody to reach the fetus before birth. This paper reviews the placental biology of primates, and discusses its involvement in adrenocortical hormone activity during pregnancy, the transfer of maternal antibody, and finally the delivery of maternal iron to the fetus, which is needed for normal brain development. An understanding of these vital functions during a full-term, healthy pregnancy provides insights into the consequences of gestational disturbances, such as maternal stress, illness, and undernutrition, which have even larger ramifications if the infant is born premature.