Evidence for decidua—trophoblast interactions in early human pregnancy

: Medium conditioned by decidual cells decreased the growth of cultured BeWo choriocarcinoma cells. The degree of inhibition was dependent on the concentration of the conditioned medium used, and suggested that maternal decidua might regulate the growth of the fetal placenta. Medium from BeWo cells and primary trophoblast had the opposing effect and increased the growth of cultured decidual cells for up to 120 h of culture. These results suggest that a regulatory loop to control placental and decidual growth exists at the materno-fetal interface, and this may be an important factor in the development of adequate placentation and the subsequent growth of the placenta during pregnancy.