trophoblast) into the maternal uterus is a vital stage in the establishment of pregnancy. Failure of the trophoblast to invade sufficiently is important in the development of some cases of pre-eclampsia. Invasion of the trophoblast too deeply may cause conditions such as placenta accreta, placenta increta, or placenta percreta. Gestational trophoblastic disease is a pregnancy-associated concept, forming from the villous and extravillous trophoblast cells in the placenta. Choriocarcinoma are trophoblastic tumors that form in the uterus from villous cells. Trophoblast stem cells (TSCs) are cells that can regenerate and they are similar to embryonic stem cells (ESCs) in the fact that they come from early on in the trophoblast lifetime. In the placenta, these stem cells are able to differentiate into any trophoblast cell because they are pluripotent. Additional images See also Syncytiotrophoblast Hydatidiform mole References External links Animal developmental biology