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Exploring the facts about donating umbilical cord blood.

The umbilical cord is the lifeline to a developing fetus. Within it, one vein and two arteries provide essential two-way transport for blood, nutrients and waste products. After birth, the cord is usually tied or clamped and then cut a few inches from the newborn’s navel. Historically, doctors and midwives simply threw the severed cord away.

All that changed when studies began to show that the blood remaining in the umbilical cord and attached placenta (“cord blood” for short) could be a viable alternative to adult bone marrow for treating dozens of conditions.

What’s in cord blood?

Cord blood contains everything regular blood does. It’s also unusually rich in blood-forming cells known as hematopoietic stem cells. Because these immature cells can become red blood cells, white blood cells or blood-clotting platelets, they provide the building blocks needed to reconstruct diseased or damaged bone marrow, where blood cells are normally made.

What’s so special about cord blood?

A problem with bone marrow donations is that donor and recipient need to be very closely matched.

Nearly every cell in the body carries human leukocyte antigen (HLA) protein tags, which label cells as “self”, preventing the person’s own immune system from attacking them. Matching these tags between donor and recipient can prevent initial rejection of the transplant and minimise subsequent attacks by the transplanted cells on the new host’s cells. For a bone marrow transplant, doctors try to match ten HLA tags; many medical centres won’t attempt a transplant unless at least nine match.

Finding a good match can be hard, especially for people with a more diverse genetic ancestry (particularly those of African descent). The immune cells within cord blood, fortunately, are less strict in distinguishing “self” from “other”. If necessary, doctors can now use donor cord blood that matches only four of six prominent tags on the recipient’s cells. Those transplants, they’ve found, take just as well as fully matched blood or bone marrow from unrelated donors.

How do donations work?

Parents can consent to donate their newborn’s cord blood to a public bank, where it will be tested, anonymised and then frozen for potential future use in another child or adult. Private banks, by contrast, charge a fee to store the baby’s cord blood in case that child or another family member needs the cells as a medical treatment later on.

Not every donated unit of blood passes muster. According to Michael Boo, chief strategy officer for the National Marrow Donor Program in the US, tests and questionnaires are used to weed out blood that may be compromised by HIV, hepatitis or other infections, as with other blood donations. And there needs to be enough blood retrieved for it to merit storage.

Cord blood can be stored indefinitely in liquid nitrogen or nitrogen vapour. An early pioneer in the field found that a thawed sample still yielded viable cells after being frozen for over 23 years.

Where are cord blood banks found?

Most public cord blood banks are clustered in North America, Europe and Asia, though there are also some in Australia and South America.

In the US, the National Marrow Donor Program has maintained a cord blood registry since 1998. They have nearly 240,000 cord blood units listed in their Be The Match registry, and access to roughly 710,000 units worldwide.

In the UK, the National Health Service public cord blood bank set up shop in December 1995 and collects from six maternity hospitals. The Anthony Nolan cancer charity launched its own public cord blood-banking programme in 2008 to complement the NHS effort and collects from another four hospitals. Combined, the banks have more than 21,000 units on hand and are aiming for a total goal of 30,000 by the end of 2018.

Any controversies around banking?

One point of contention concerns a growing practice called delayed clamping, in which the umbilical cord is kept attached to the newborn for several minutes before being clamped and removed. Some studies have suggested that this delay increases the transfer of iron-rich blood to the baby and can yield long-term benefits, including improved social and fine motor skills. Other researchers have taken a more cautious stance on the advantages, and the question of precisely when to clamp the cord remains unsettled.

Leaving the cord attached too long may significantly reduce the volume of blood that can be donated. “We have to find what is the right timing for the baby, and then not go any further than we need to,” Boo says. “If it’s over ten minutes, it clearly impacts collectability. If it’s between two and five, not so much, and we need more studies to understand that better.”

Is a cord blood transplant worth the costs?

Disagreements persist over some of the relative costs and benefits of cord blood transplants. In a 2016 study led by Filippo Milano and Colleen Delaney at the Fred Hutchison Cancer Research Center in Seattle, such transplants outperformed all other options in lowering the risk of leukaemia relapse for patients whose disease hadn’t been entirely eradicated before the transplant. On average, however, cord blood transplants still require more time to take hold in recipients.

They’re not cheap either – a cord blood unit can run to as much as $45,000 – though if use becomes more widespread, this might eventually help banks drive down transplant costs. In the meantime, says Mary Laughlin, medical director of the Cleveland Cord Blood Center in Ohio, hospitals and insurers often balk at the higher upfront expenditures but overlook the subsequent benefits for diseases like leukaemia. “They’re not focusing on the reason why you did the transplant, which is to clear the leukaemia,” she says. 

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