Like most fathers nowadays, I was present when both my boys were born. I remember the delivery of the placenta (commonly called the afterbirth) after each baby was born but I took no interest in it, being too preoccupied with checking that my little darlings were fully equipped with fingers and toes, etc.
The placenta and umbilical cord were discarded as waste biological tissue. It is now realised that the blood in the placenta and umbilical cord is a rich source of stem cells which can be used very successfully to treat leukaemia and various blood disorders, mainly in young children (described by Ronald Kline in Scientific American, April 2001).
The placenta is an organ which forms in the womb during pregnancy and is composed of maternal and embryonic tissue. It is connected to the foetus through the umbilical cord, which provides oxygen and nutrients and removes waste products from the foetus to the maternal blood.
Blood contains several types of cells, principally white cells, red cells and platelets. White cells are an important part of our immune defence system and they attack and destroy invading foreign bodies. Red cells carry oxygen from the lungs and carry waste carbon-dioxide from the tissues back to be exhaled through the lungs. Platelets cause blood to clot, sealing the circulation system after it is wounded. All these cells are made from stem cells in the bone marrow.
Leukaemia is a cancer which affects white blood cells, causing them to proliferate in an uncontrolled manner. They crowd into the bone marrow and suppress the blood-forming apparatus. The abnormally dividing white cells can be killed by chemical treatment (chemotherapy) but the blood system must be rebuilt, which in some cases must be done by transplanting in a population of healthy stem cells.
In the past, medicine relied on transplants of bone marrow from living donors. Unfortunately, this often entails a long wait while a suitable donor is identified, leaving the leukaemia patient at serious risk. Also complications often arise because the donor marrow is not well matched to the recipient.
Physicians have recently realised that transplantation success rates could be dramatically improved by using stored blood from afterbirths rather than bone marrow.
Our body cells have a molecular arrangement on their surfaces which is characteristic for each of us. Our immune system recognises our characteristic surface molecular arrangements as "self" and does not attack our own cells. However, it will attack invading agents not protected by our own characteristic molecular code. This produces a perennial problem for transplantation techniques: how to prevent the recipient rejecting a donated organ.
Luckily, the molecular surface signatures of cells come in a limited number of variations and it is possible to approximate a match between the donor and recipient. The match-up is never perfect and this often leads to complications in bone marrow transplantations. However, this problem is very much reduced when blood from afterbirths is used because stem cells from this source are tolerated much better by immune systems.
Leukemia is not the only disease which can be treated by rebuilding the blood-forming system. The stem cells from afterbirth blood can also restore normal red cells in people with sickle cell anaemia (where the red cells are abnormal in shape and function) and can reform the immune system in babies born with a severely deficient immune response.
When any new technology is introduced it carries its own risks and ethical problems and using blood from afterbirths is no exception. One possible problem is that the stem cells in afterbirth blood might have a genetic defect whose consequences do not reveal themselves in the donor for months or even years.
A most interesting ethical problem which can arise is illustrated by a recent Californian case. A young girl, Molly, was diagnosed to have a potentially fatal blood disease called Fanconi anaemia. Her parents decided to conceive another child in order to use the afterbirth blood to treat Molly.
The new child, Adam, was conceived by in-vitro fertilisation. Physicians screened embryos from the mother prior to implantation into her womb to pick one free from the disease and a good tissue match for Molly. The transplant of afterbirth blood from Adam to Molly saved her life, but was the whole procedure ethical?
A panel of bioethicists decided that the procedure was ethical because donating the blood would have no effect on Adam's health. On the other hand, Adam might never have been born had his sister not been sick. If Adam was deliberately conceived in order to provide tissue for his sister, would this be ethical?
The ideal situation is that every child is conceived out of love and raised as an autonomous individual. On that basis one might quibble with what Molly's parents did. However, I feel that the good accomplished in this case so greatly outweighs the reservations that the procedure was justified. Faced with the same circumstances, I would probably make the same decision myself.
William Reville is a senior lecturer in biochemistry and director of microscopy at UCC