Amniotic stem cells are the mixture of stem cells that can be obtained from the amniotic fluid as well as the amniotic membrane. They can develop into various tissue types including skin, cartilage, cardiac tissue, nerves, muscle, and bone. The cells also have potential medical applications, especially in organ regeneration.

The stem cells are usually extracted from the amniotic sac by amniocentesis which occurs without harming the embryos. The use of amniotic fluid stem cells is therefore generally considered to lack the ethical problems associated with the use of cells from embryos.

The presence of embryonic and foetal cells from all germ layers in the amniotic fluid was gradually determined since the 1980s. Haematopoietic progenitor cells were first reported to be present in the amniotic fluid in 1993, specifically up to the 12th week of pregnancy. It was suggested that these originated from the yolk sac.

In 1996, a study indicated that non-haematopoietic progenitor cells were also present in the amniotic fluid. This was later confirmed as mesenchymal stem cells were obtained. In addition, evidence indicated that embryonic stem cells are part of the fluid, although in very small quantities.

At around the same time, it was determined that stem cells from the amniotic membrane also have multipotent potential. AS their differentiation into neural and glial cells as well as hepatocyte precursors was observed.

The majority of stem cells present in the amniotic fluid share many characteristics, which suggests they may have a common origin.

In 2007, it was confirmed that the amniotic fluid contains a heterogeneous mixture of multipotent cells after it was demonstrated that they were able to differentiate into cells from all three germ layers but they could not form teratomas following implantation into immunodeficient mice. This characteristic differentiates them from embryonic stem cells but indicates similarities with adult stem cells. However, foetal stem cells attained from the amniotic fluid are more stable and more plastic than their adult counterparts making it easier for them to be reprogrammed to a pluripotent state.

A variety of techniques has been developed for the isolation and culturing of amniotic stem cells. One of the more common isolation methods involves the removal of amniotic fluid by amniocentesis. The cells are then extracted from the fluid based on the presence of c-Kit. Several variations of this method exist. There is some debate whether c-Kit is a suitable marker to distinguish amniotic stem cells from other cell types because cells lacking c-Kit also display differentiation potential. Culture conditions may also be adjusted to promote the growth of a particular cell type.