Down syndrome’s new pregnancy blood test, which could potentially save miscarriages, may soon be determined by cfDNA.
Presently, women can have a pregnancy blood test between 11th and 13th week of pregnancy to find out if her baby has down syndrome or other fetal abnormalities. The tests involve an ultrasound scan and blood test, and from there, the expecting mother can decide whether she wants to have more invasive tests like amniocentesis and CVS; but this may put the baby at risk.
Currently, women are faced with invasive procedures like amniocentesis to see if the fetus has genetic diseases and CVS (chorionic villus sampling) which samples a tiny piece of the placenta by inserting a tin plastic tube through the cervix where a needle is inserted to take samples. Amniocentesis is a prenatal test done by removing a small amount of amniotic fluid from the sac surrounding the fetus for testing by inserting a needle into the belly to pull the fluid. Sample materials are then taken into the laboratory for genetic testing, which will take about two weeks.
Since either test may put the mother and child at risk, it is currently recommended for women with significant risk of genetic disease, including those who have a family history of the disease, have had a pregnancy with birth defects, have an abnormal ultrasound, and will be 35 or older at the time of delivery, to undergo amniocentesis. While amniocentesis has about 99.4%, chance that it could cause a miscarriage, it is, nevertheless, 1 in 200 to 1 in 400.
At the moment, the only tests available to diagnose down syndrome are the screening test to estimate your baby’s chance of having the disease, and diagnostic tests such to give you definitive results if your baby has chromosomal condition.
However, the new pregnancy blood test may provide non-invasive options for expectant mothers during their first trimester of pregnancy and prevent miscarriages. Dr. Kypros Nicolaides and fellow researchers at the Harris Birthright Research Centre for Fetal Medicine at King’s College London in the U.K. have developed a superior way of screening for Down syndrome, and have found that cfDNA tests are far more accurate.
Down syndrome is a condition also known as trisomy 21, which is one of the most common genetic causes of learning disability. It is caused by the presence an extra copy of chromosome 21 in the baby’s cells that occurs at conception. While this is considered a genetic disorder that causes lifelong developmental delays, intellectual disability, and other health problems, most of the time it is not inherited, but caused by a mistake in cell division during development.
Various studies have suggested that Cell-free DNA (cfDNA) is a non-invasive test that analyses the traces of DNA circulating in the mother’s blood. This test is superior compared to currently available tests because it can accurately detect fetal abnormalities. The cfDNA test has a low rate of “false positives” which is 0.1% compared to 4.3% for the other combined tests.
Following the success of cfDNA, the new down syndrome pregnancy blood test that may save miscarriages, it will be offered next month by two UK hospitals for free.
Written by: Janet Grace Ortigas