Skip to main content
Wolfson Institute of Preventive Medicine - Barts and The London

In-house Antenatal reflex DNA screening for Down’s syndrome, trisomy 18 and trisomy 13


The Wolfson Institute of Preventive Medicine with the assistance of Premaitha Health plc, is launching an in-house antenatal reflex DNA screening service on 19 October 2015. The DNA screening test estimates the risk of having a pregnancy with Down’s syndrome, trisomy 18 (Edwards syndrome) or trisomy 13 (Patau syndrome) by analysing cell free DNA from a sample of maternal blood.

The reflex DNA screening service at the Wolfson Institute started in April 2015. Previously blood samples were sent to the United States for DNA analysis. Now the DNA analyses are to be performed in a new laboratory at the Wolfson Institute set up using Premaitha’s test methodology.

The reflex DNA screening approach involves taking two blood samples between 11 and 13 weeks of pregnancy. One sample is tested using the current Combined test and the other is held for possible DNA analysis which is done automatically if the Combined test indicates a risk of having an affected pregnancy that is equal to or greater than 1 in 800. About 10% of women screened will have a reflex DNA test in this way. Importantly the reflex approach avoids the need to recall women for a second blood test and so avoids causing unnecessary anxiety. The screening method detects about 9 in 10 affected pregnancies with a false-positive rate of less than 1 in 1,000. A positive screening result leads to an offer of a diagnostic test (a chorionic villus sampling or an amniocentesis).

Use of the Premaitha DNA analysis platform set up within the Wolfson Institute provides a DNA screening service “in-house” avoiding the need to send blood samples to overseas laboratories. The in-house facility at the Wolfson is, to our knowledge, the first such service performing reflex DNA screening.

Please follow this link to see the publication on Performance of antenatal reflex DNA screening [PDF 457KB]
Please click here to see our information leaflet on Antenatal Reflex DNA Screening [PDF 603KB]