<P> From 24 to 34 weeks of gestation, when the fetus is typically viable, blood can be taken from the cord in order to test for abnormalities (particularly for hereditary conditions). This diagnostic genetic test procedure is known as percutaneous umbilical cord blood sampling . </P> <P> The blood within the umbilical cord, known as cord blood, is a rich and readily available source of primitive, undifferentiated stem cells (of type CD34 - positive and CD38 - negative). These cord blood cells can be used for bone marrow transplant . </P> <P> Some parents choose to have this blood diverted from the baby's umbilical blood transfer through early cord clamping and cutting, to freeze for long - term storage at a cord blood bank should the child ever require the cord blood stem cells (for example, to replace bone marrow destroyed when treating leukemia). This practice is controversial, with critics asserting that early cord blood withdrawal at the time of birth actually increases the likelihood of childhood disease, due to the high volume of blood taken (an average of 108ml) in relation to the baby's total supply (typically 300ml). The Royal College of Obstetricians and Gynaecologists stated in 2006 that "there is still insufficient evidence to recommend directed commercial cord blood collection and stem - cell storage in low - risk families". </P> <P> The American Academy of Pediatrics has stated that cord blood banking for self - use should be discouraged (as most conditions requiring the use of stem cells will already exist in the cord blood), while banking for general use should be encouraged . In the future, cord blood - derived embryonic - like stem cells (CBEs) may be banked and matched with other patients, much like blood and transplanted tissues . The use of CBEs could potentially eliminate the ethical difficulties associated with embryonic stem cells (ESCs). </P>

When did we start cutting the umbilical cord