Page URL:

Fetal DNA scanned for disease

13 December 2010
Appeared in BioNews 588

Scientists have scanned the entire DNA of an unborn child from the mother's blood sample for the first time to safely check for genetic disorders. The new technique, developed by Dr Dennis Lo from the Chinese University of Hong Kong, was tested in a couple being screened for an inherited blood disease called beta-thalassemia, a form of anaemia.

The complex procedure involved sequencing almost four billion DNA molecules from the pregnant mother's blood sample and separating the fetal DNA strands buried deep within it. They were then able to piece together a genome-wide genetic map of the fetus by using the genetic maps of both the parents, which highlighted places where the inherited DNA differed in the fetus.

Finally, the completed fetal genetic map was scanned for genetic disorders and researchers found that the baby had inherited the beta-thalassemia mutation from the father, and was therefore a carrier of the disease. 'Our study suggests the feasibility of using genome-wide scanning to diagnose fetal genetic disorders pre-natally in a non-invasive way', the researchers said.

At the moment, prenatal testing of genetic diseases relies on invasive methods, which require taking a tissue sample from the placenta (CVS) or removing amniotic fluid from the womb (amniocentesis) with an injection. These techniques involve a one percent risk of triggering a miscarriage or infection and are therefore only carried out in cases where the probability of disease is high.

In 1997, it was discovered that some of the fetus' DNA circulates in the mother's blood stream. The researchers of this new study observed that 'uncovering the fetal genome amongst floating DNA is technologically akin to finding a needle in a haystack', because the DNA of the baby makes up only ten percent of the total genetic mixture of the blood.

This study raises the possibility that non-invasive fetal genetic testing may eventually be possible. However, more development and testing of this novel technique will be needed before it could replace existing clinical methods. The new approach also raises a number of ethical, legal and social issues that require active discussion among clinicians, scientists, ethicists and the community.

Dr Christine Patch, Consultant Genetic Counsellor at Guy's Hospital in London, said: 'While this is a potentially interesting approach that may have benefit for some families with serious genetic disorders who are making difficult choices when having children, there are many concerns'.

'Before such a test could be offered in the clinic, a much larger study is required to determine the robustness of the technique, and numerous logistical, economic and ethical issues need to be addressed including how to deal with unexpected or incidental findings', added Dr Caroline Wright, Head of Science at the Public Health Genomics Foundation.

'Tests like this may produce clinically useful information, but they may also be a cause of unnecessary worry and anxiety; or they may offer false reassurance in a pregnancy that has serious non-genetic abnormalities that will not be picked up by the test', explained Dr Patch. 'We do not randomly test pregnancies for a long list of other conditions that may only manifest in adult life on the basis that individuals may not want to know that information when they are older'.

The study was funded by the Hong Kong Research Grants Council, Sequenom Incorporated from the US, the Chinese University of Hong Kong, and the Government of the Hong Kong Special Administrative Region, China. The research was published in the journal Science Translational Medicine. 

Babies' DNA profiled in the womb
Telegraph |  9 December 2010
Early work on baby screening blood test
NHS Choices |  12 December 2010
Genetic screening breakthrough
Nursing Times |  9 December 2010
Maternal Plasma DNA Sequencing Reveals the Genome-Wide Genetic and Mutational Profile of the Fetus
Science Translational Medicine |  8 December 2010
Mother's blood test could be used to predict disorders in unborn baby
Daily Mail |  9 December 2010
22 June 2015 - by Ceri Durham 
A US federal appeals court has upheld a ruling that Sequenom's prenatal MaterniT21 test is not sufficiently 'inventive' to be patentable....
23 June 2014 - by Dr Anna Cauldwell 
Two patients with the serious inherited blood disorder beta-thalassemia have been able to stop blood transfusions 12 days after receiving experimental gene therapy...
7 April 2014 - by Rebecca Carr 
The American College of Medical Genetics and Genomics (ACMG) has updated its position on the return of results from genome sequencing to allow patients to opt out from receiving incidental information....
14 January 2013 - by Dr Daniel Grimes 
US biotech company Verinata Health has reported sequencing fetal DNA taken from pregnant women's blood to test for genetic abnormalities...
10 December 2012 - by Dr Lux Fatimathas 
More sensitive prenatal testing of fetal DNA could improve the detection of genetic diseases, studies find...
7 June 2010 - by Rosemary Paxman 
A newly identified genetic defect may help reduce fetal abnormalities such as Meckel-Gruber and Joubert syndromes, according to a new study in the journal Nature Genetics....
16 February 2009 - by Dr Philippa Brice 
Cell-free fetal nucleic acids - DNA or the related molecule RNA - are present in the blood. As has previously been reviewed, the discovery that a small proportion of the cell-free nucleic acids in the mother's blood during pregnancy actually comes from the fetus paved the way for new techniques to exploit...
8 December 2008 - by Evelyn Harvey 
By Evelyn Harvey: A new method for early detection of genetic diseases in unborn babies using a simple blood test can detect the inherited condition beta-thalassemia, according to a study published in Proceedings of the National Academy of Sciences. Although the technique, which analyses cell free fetal DNA (cffDNA) present...
to add a Comment.

By posting a comment you agree to abide by the BioNews terms and conditions

Syndicate this story - click here to enquire about using this story.