Until now, for it to be determined if a child will be born with Down’s syndrome, invasive procedures needed to be conducted, however a new study finds that women in high risk pregnancies for Down’s syndrome could have a DNA blood test to detect the disorder and avoid invasive procedures. Such procedures include amniocentesis, which requires a puncture of the amniotic sac, or chorionic villus sampling or a removal of a small piece of placenta tissue (chorionic villi) from the uterus during early pregnancy.

These tests carry a 1% risk of miscarriage and are therefore reserved for high risk pregnancies. Invasive testing still takes place in 3-5% of pregnant women in the United Kingdom for example.

However, in an international broad study led by Professor Dennis Lo from The Chinese University of Hong Kong found that a simple blood test could be used to accurately rule out Down’s syndrome among high risk pregnancies before the consideration of amniocentesis or chorionic villus sampling, eliminating close to 98% of such procedures.

The test uses the latest DNA technology to analyze genetic components in the mother’s blood that indicate whether the fetus has Down’s, or trisomy 21. Chromosomes are holders of genes, the bits of DNA that direct the production of a wide array of materials the body needs. This direction by the gene is called the gene’s “expression.” In trisomy 21, the presence of an extra set of genes leads to over expression of the involved genes, leading to increased production of certain products. For most genes, their over expression has little effect due to the body’s regulating mechanisms of genes and their products, but the genes that cause Down syndrome appear to be exceptions.

The research team used the most up-to-date DNA technology to test the blood samples from 753 pregnant women with high risk of genetic Down’s syndrome, based in Hong Kong, the UK and the Netherlands. Eighty-six (11.4%) of the women were found to be carrying a fetus with Down’s syndrome.

Down’s syndrome or trisomy 21 occurs in around 1 in 800 births and older women are at higher risk. Incidence jumps dramatically after the mother’s age of 38 years.

Women in high risk groups tend to undergo a combination of scans and hormone level tests in order to determine if they need to have an invasive testing.

Study Authored By: Professor Rossa Chiu, Li Ka Shing Institute of Health Sciences and Department of Chemical Pathology, The Chinese University of Hong Kong, Hong Kong, China

Written by Sy Kraft, B.A.