[aruanan]

Technically, umbilical cord blood, amniotic cells and placental cells are all sources of ethical fetal stem cells.

The correct terms are pluripotent and multipotent stem cells. The embryonic stem cells obtained from embryos from a few days up to 8 weeks old are pluripotent stem cells. Those stem cells available in cord blood, amniotic fluid, and placenta, are multipotent stem cells. Back in 2007 scientists discovered a way to induce an adult cell to reprogram itself back into a pluripotent cell. A non-embryonic stem cell is an "adult" stem cell. This includes those found in cord blood, amniotic fluid, and placentas.

[hocndoc]

Not all stem cells derived from the embryo up to 8 weeks old are pluripotent. It is true that embryos are defined in human embryology as up to 8 weeks old.

However, the cells commonly referred to as embryonic stem cells are usually derived when there are at least 2 cell types in the embryo, the trophoblasts and the inner cell mass. The trophoblasts aren’t pluripotent.

It does appear that they are up to the 8 cell stage or so - so pluripotent in fact that we get identical quadruplets!