Today there are about ten businesses in the UK offering to freeze and store cord blood and industry insiders estimate that up to 100,000 parents have chosen to do so in the UK. The global stem-cell market is forecast to treble to a staggering £40 billion by 2015.

Cord blood contains embryonic stem cells. They can be made into more specialised cells and can reproduce copies of themselves almost indefinitely. There is currently research into a host of applications – from growing new organs to curing paraplegia. In theory, stem cells treat disease by replacing damaged or diseased cells. They are used in bone-marrow transplants to treat leukaemia – but in these cases, donor blood taken in the usual way is used to harvest the stem cells.

To bank cord stem cells, the cord blood is extracted minutes after the birth of the baby and rushed by courier to be processed. Any cells that could be of future value are frozen at minus 180C and can then be stored for 25 years.

There are no published examples of a child’s own cord blood being used to cure them of leukaemia – one of the most common childhood diseases mentioned by the banks in their sales pitches. There are two cases of successful sibling transplants for children with the hereditary condition thalassemia, where the body makes an abnormal form of haemoglobin – the protein in red blood cells that carries oxygen. These were carried out in Singapore and Germany.

Lavish promises of future treatments tend to be based on preliminary clinical trials – and should a child fall ill today, in many cases the technology doesn’t exist to actually use the harvested stem cells. In fact, some experts believe that reintroducing banked cord blood into a child could increase the chance of relapse – as disease-causing cells that existed from birth would be stored alongside useful stem cells.

‘Parents are worried that by not storing cord blood, they aren’t giving their child the best possible chance for future health,’ says leading consultant gynaecologist and obstetrician Mr Dickinson Cowan, who admits that when he first came across private banking, he thought it was a good idea. ‘I’d never recommend it now,’ he says.