Cord blood myths

My delivery experience will be affected if I donate cord blood.

Cord blood is collected after the delivery of the baby and before the expulsion of the placenta.

After the cord is clamped and cut, umbilical cord blood is collected from the umbilicus vein of the section of cord that remains attached to the placenta. It is painless, takes only a few minutes and is done only after the baby has been safely delivered.

Stem cells are precious and should be kept only for the family.

The vast majority of the 40,000 cord blood transplants that have been performed around the world used donated cord blood from public cord blood banks.

According to the American Society for Blood and Marrow Transplantation, "the probability of using one's own cord blood is very small - probably as low as 0.04 per cent to 0.0005 per cent".

Transplant physicians may not feel that the patient's own cord blood is the best choice, as it may carry the genetic abnormality that led to the blood or immune system failure or cancer in the first place.

The public cord blood bank requires a high amount of stem cells from the cord blood to qualify for storage. The high number of cases of cord blood being discarded is a waste.

Public cord blood banks, such as the SCBB, adhere to international public cord blood banking criteria to ensure that the collected cord blood is of high quality and safe for use. These standards include a minimum cell count. At the SCBB, other than cell count, all collected cord blood units are evaluated for blood volume, cell viability and infectious diseases, along with other tests.

Cord blood units that do not meet the requirements may be assigned for approved research, if the mother had agreed to that. Otherwise, it will be discarded according to hospital protocol.

Taking blood samples from the mother will result in anaemia after the baby's birth.

The collection of maternal blood samples is done before delivery, when the mother is admitted to the labour ward or delivery suite. These blood samples are critical to ensure the safety of the donated cord blood. About 30ml of blood is collected from the mother. This is less than 1 per cent of a person's blood volume and has not led to any reported case of anaemia in mothers.

Blood type is used to match a cord blood donor and a patient.

Human leukocyte antigen (HLA) typing, not blood type, is used to match a patient with a cord blood donor. HLA is a protein - or marker - found on most cells in our body.

Our immune system uses HLA markers to find out which cells belong in our body. Donated cord blood units that are banked at the SCBB are tested for HLA. The results are stored in the SCBB's Public Cord Blood Registry, so that they can be searched when a patient requires a cord blood unit.

Transplant physicians review at least six HLA markers to find a match. A cord blood unit requires at least four of six matched markers (67 per cent similarity) to qualify for a transplant.

A closely-matched HLA between the donor and patient increases the probability of a successful transplant, improves engraftment - when the patient's body accepts the stem cells and starts to produce new cells - and reduces the risk of complications.

Poon Chian Hui

•Source: Associate Professor Tee Chee Seng, senior consultant, division of obstetrics and gynaecology, KK Women's and Children's Hospital

A version of this article appeared in the print edition of The Straits Times on December 15, 2015, with the headline 'Cord blood myths'. Print Edition | Subscribe