ectoplacental

ec·to·pla·cen·tal

(ek'tō-plă-sen'tăl),
1. Outside, beyond, or surrounding the placenta; in primates, referring especially to the parts of the trophoblast not directly involved in the formation of the placenta.
2. In rodents, referring to the actively growing part of the trophoblast involved in the formation of the placenta.