[Chorionic gonadotropin (beta-HCG) in the amniotic fluid in normal pregnant women]

Human chorionic gonadotropin beta subunit (beta-HCG) was measured in amniotic fluid and radioimmunoassay levels compared with those obtained in plasma from normal pregnant women. Amniotic beta-HCG exhibited a secretory pattern similar to that seen in the plasma compartment. Nonetheless amniotic beta-HCG had an elevation peak later than its plasma counterpart, with a progressive decrease that persisted throughout gestation without reaching a nadir as it occurred in plasma. Such a pattern of HCG production contained in the amnion is compatible with an HCG conformation released by the syncytiotrophoblast.