Fetal adrenal medulla.

The development of the fetal adrenal medulla can be considered an integral part of the complex process of maturation and preparation of the fetus for extrauterine life. Our understanding of the fetal sympathoadrenal function is facilitated by the relative separation that exists between the maternal and fetal catecholamine secretion and metabolism. There is accumulating evidence that the catecholamines fulfill a vital role at the time of delivery by controlling nonshivering thermogenesis and cardiovascular regulatory mechanisms. They also may play a role in the carbohydrate metabolism by triggering the neonatal glucagon surge, known to be important to the augmentation of hepatic glucose output in the newborn. Though the role of epinephrine in the adaptation of the human neonatal lung to extrauterine life remains to be defined, it may be extrapolated from experimental data that the secretion of surfactant from type II alveolar cells is dependent on epinephrine. Additional studies are needed to broaden our understanding of the process of adrenal medullary maturation and responses in the fetus. Further studies will have to e done to define all the roles the catecholamines play in fetal life. The refinement of methodology in recent years will facilitate this task. It is our belief that in the near future catecholamine determinations will be utilized to quantify and evaluate fetal stress in conjunction with biophysical assessments.