Pregnant Women Should Not Eat Soy Products

A high estrogenic environment in utero may increase subsequent breast cancer risk. It was therefore determined whether a maternal exposure during pregnancy to the phytoestrogen genistein, which exhibit estrogenic activities in vitro and in vivo, alters breast cancer risk among female offspring. The results indicate that in utero exposure to genistein, dose-dependently increased the incidence of breast tumors, when compared with the controls. The number of estrogen receptor binding sites was significantly elevated in the mammary glands of genistein offspring.

Oncol Rep 1999 Sep-Oct;6(5):1089-95