Perinatal stem cells are those derived right before or after birth. They include those derived from the umbilical cord blood and tissue, placental blood and tissue, and the amniotic tissue and amniotic fluid.
What are Perinatal Stem Cells?
However, when stem cells were first identified, only two types of stem cells were described, adult stem cells and embryonic stem cells. The reason a diverse range of stem cell types now exist is that human embryonic stem cells (hESCs) have become further characterized, the diversity of adult stem cell types has substantially expanded and induced pluripotent stem cells (iPSCs) have since been discovered.
Now, researchers debate the number of stem cells in existence, because the number depends on whether stem cells are characterized functionally (for example, neural stem cells, mesenchymal stem cells, and hematopoietic stem cells) or characterized by source tissue (for example, cord blood stem cells, dental pulp stem cells, and amniotic stem cells).
What is clear is that a wide range of stem cell types now exists, which has added substantial complexity to the stem cell landscape.