Earlier Down's Syndrome Testing May Provide New Glimpse into Condition, More Accuracy

A new study shows that the earlier a baby's DNA is analyzed while in the womb, the more accurate the results can be when testing for Down's syndrome.  

According to the study, researchers from the King's College of London looked at over 750 babies who were born with the condition, also known as trisomy 21, which is one of the most common genetic causes for a learning disability.

The Mayo Clinic notes that Down's syndrome is a genetic disorder that causes lifelong mental retardation, developmental delays and other problems, which range in severity from moderate to serious. It is the most common genetic cause of a learning disability seen in children, and understanding the condition along with early interventions can make a big difference in the lives of both children and adults with the health issue.  

Testing for Down's syndrome currently involves various exams used between the 11^th and 13^th week of pregnancy, that involve an ultrasound scan and a blood test. These give an estimate of the baby having Down's syndrome.

Results following this test thus determine whether or not a more invasive procedure is needed, which can result in miscarriage. They are corionic villus sampling (CVS), which samples a small piece of the placenta, and amniocentisis, which tests the amniotic fluid around the baby. 

Several studies have already suggested that non-invasive genetic tests that use fetal cell free DNA (cfDNA) from a pregnant woman's blood can be highly sensitive and specific.

This latest study from Nicolaides and colleagues is the first to look at the feasibility of using such a cfDNA test for trisomy 21 and other chromosomal disorders.

Their results, obtained from tests carried out in 1,005 pregnancies at 10 weeks, showed a lower rate of "false positives" and higher sensitivity than the combined test done at 12 weeks.

"This study has shown that the main advantage of DNA testing, compared with the combined test, is the substantial reduction in false positive rate," the authors note, according to the study. "Another major advantage of cfDNA testing is the reporting of results as very high or very low risk, which makes it easier for parents to decide in favor of or against invasive testing."

The findings for the study are published online in June 7 issue of Ultrasound in Obstetrics & Gynecology,