Can a blood test predict your health future?

Lo had discovered a "treasure trove" of valuable DNA floating freely in the bloodstream.
His breakthrough would one day make it possible for pregnant women to safely screen their unborn children for genetic conditions, to map out the entire genome of their fetus, and potentially screen all ages for cancer at its earliest stages.
All using a simple blood test.
Lo's first discovery was that the DNA of an unborn baby floats freely in its mother's blood plasma -- the yellow liquid that holds blood cells in suspension.
That DNA, he knew, was a window into an unborn baby's health, and future.
But, at the time of his discovery, the medical world wasn't interested.
"They thought that you could only use it for sex selection," says Lo, now the Director of the Li Ka Shing Institute of Health Sciences, in Hong Kong. This was deemed by experts to be a narrow application and one filled with ethical problems, according to Lo.
The medical world had missed what would become one of the 21st century's biggest breakthroughs.
But this didn't stop Lo.
His beginnings
Lo's quest to find fetal DNA in the mother's blood had begun at Oxford University, where he met pioneering scientist Professor John Bell.
"I heard him give a lecture about the polymerase chain reaction (PCR). He said this technique would change the world," recalls Lo, now 52.
PCR is a technique used to amplify a single piece of DNA into thousands, or even millions, of copies.
Lo learned how to use the cutting-edge technology, and soon after searched for a way to apply it.
His goal? A safer, non-invasive, test for Down syndrome.
Removing the risks
The traditional test for many mothers-to-be was to undergo a procedure called amniocentesis, where fluid is extracted from the amniotic liquid surrounding a baby in the womb. The cells within the fluid are then screened for health conditions, such as Down syndrome.
"A big needle had to be inserted through the mother's tummy into the uterus," says Lo.
The procedure carries an estimated 1 in 100 chance of causing a miscarriage, according to the UK National Health Service.
"I wondered, why did doctors do such a dangerous procedure? How about [we] just take a blood sample from the mother?" says Lo.
Science, however, had to catch up with his ambition: During this time as a student in the 1980s, the blood of a baby and its mother were believed to be separate.
Lo began an eight-year search for fetal DNA inside a mother's blood cells. But the number of fetal cells that enter this part of the maternal blood turned out to be very small, and the search had to be called off.
In 1997, it was time for a change.
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