Maternal and neonatal phytoestrogens in Japanese women during birth.

Abstract Objective: High levels of soy isoflavonoids among adult Japanese persons are associated with a low incidence of hormone-dependent cancers, but nothing is known about isoflavonoids in pregnancy. Study Design: We studied 7 young healthy Japanese women at delivery by measuring 6 phytoestrogen metabolites in maternal and cord plasma and in amniotic fluid. Results: Total maternal plasma isoflavonoid concentrations ranged from 19 to 744 nmol/L (mean 232 nmol/L), cord plasma values ranged from 58 to 831 nmol/L (mean 299 nmol/L), and amniotic fluid values ranged from 52 to 779 nmol/L (mean 223 nmol/L). Maternal and cord plasma and amniotic fluid lignan values were low. Conclusions: The high levels of isoflavonoid phytoestrogens found in healthy neonatal Japanese infants indicate transfer of isoflavonoids from the maternal to the fetal compartment. These compounds may modify estrogen metabolism and action during fetal life and perhaps affect cancer risk. (Am J Obstet Gynecol 1999;180:737-43.)