Question: What are fetal stem cells?
About the article "Stem cell", section "Fetal".

Candidate passages:
The primitive stem cells located in the organs of fetuses are referred to as fetal stem cells.
There are two types of fetal stem cells:
 Fetal proper stem cells come from the tissue of the fetus proper, and are generally obtained after an abortion.
These stem cells are not immortal but have a high level of division and are multipotent.
 Extraembryonic fetal stem cells come from extraembryonic membranes, and are generally not distinguished from adult stem cells.
These stem cells are acquired after birth, they are not immortal but have a high level of cell division, and are pluripotent.
Stem cell treatments may require immunosuppression because of a requirement for radiation before the transplant to remove the patient's previous cells, or because the patient's immune system may target the stem cells.
One approach to avoid the second possibility is to use cells from the same patient that is being treated.
Pluripotency in certain stem cells could also make it difficult to obtain a specific cell type.
It is also difficult to obtain the exact cell type needed, because not all cells in a population differentiate uniformly.
Undifferentiated cells can create tissues other than desired types.
Some stem cells form tumors after transplantation; pluripotency is linked to tumor formation especially in embryonic stem cells, fetal proper stem cells, induced pluripotent stem cells.
Fetal proper stem cells form tumors despite multipotency.
Hepatotoxicity and drug-induced liver injury account for a substantial number of failures of new drugs in development and market withdrawal, highlighting the need for screening assays such as stem cell-derived hepatocyte-like cells, that are capable of detecting toxicity early in the drug development process. 
ReNeuron is a UK-based stem cell research company, whose shares are listed on the Alternative Investment Market.
Its focus is on the development of stem cell therapies targeting areas of poorly met medical need, including peripheral arterial disease, stroke, and retinal diseases.
ReNeuron is currently testing the effects of neural stem cells on spines for neuroregeneration.
They are also testing the use of fetal stem cells on stroke patients. 
  Foreign genes or mutations can be introduced into ES cells rather easily, and these ES cells can then be grown into whole animals using the tetraploid complementation assay.
By introducing targeted mutations into the tetraploid cells and/or into the ES cells, one can study which genes are important for fetal development and which ones are important for development of the extra-embryonic tissues.
The tetraploid complementation assay is also used to test whether induced pluripotent stem cells (stem cells artificially produced from differentiated cells, e.g.
from skin cells) are as competent as normal embryonal stem cells.
If a viable animal can be produced from an induced pluripotent stem cell using the tetraploid complementation assay, then the induced stem cells are deemed equivalent to embryonal stem cells.
This was first shown in 2009.  
The public in the United States has a general awareness of embryonic stem cells because of the stem cell controversy.
However, cord blood stem cells (hematopoietic stem cells) are not embryonic stem cells (pluripotent stem cells).