Scientists have found a safer approach for diagnosing Down syndrome and other genetic disorders that may one day become available using a genetic test performed on blood taken from pregnant women.
Stephen Quake of Stanford University in California and a team of researchers have found a way to look for the extra chromosomes that cause Down syndrome and similar birth defects in the tiny amounts of fetal DNA that circulate in the mother's blood.
The new technique which requires only a sample of the mother's blood could prove less risky than other prenatal tests used to look for Down syndrome and other chromosomal disorders.
Current prenatal gene tests include amniocentesis and chorionic villus sampling (CVS) uses amniotic fluid extracted from the uterus and poses risk of infection and miscarriage.
Researchers are hopeful that the test will detect Down syndrome earlier in the pregnancy. It may also help detect other genetic disorders like Patau Syndrome and Edward Syndrome.
Down syndrome, the most common genetic cause of mental retardation and other problems, affects one of every 733 babies born in the U.S., according to the National Down Syndrome Society.
“The ability to diagnose fetal chromosomal disorders from maternal blood is an important advancement in the area of prenatal diagnosis,” said Dr. James Goldberg of Perinatal Associates Inc. This new approach “would omit the risk of fetal loss associated with invasive procedures such as amniocentesis.”
More research is needed to confirm the findings and to test the method's accuracy and reliability. Other promising approaches have failed to hold up during further testing.
The new approach scans aneuploidy, an abnormality in the number of chromosomes. Typically, humans inherit 46 chromosomes, half from each parent. Errors in chromosomes can cause serious problems in mental and physical development. For instance, Down syndrome arises from an extra copy of chromosome 21.
The study involved blood samples from 18 women and one man for comparison. The samples were drawn when the women were 10 to 35 weeks pregnant, after standard testing such as amniocentesis was performed.
Researchers were able to accurately diagnose nine cases of Down syndrome, two cases of another genetic disorder, Trisomy 18 (also known as Edward syndrome) and one case of Trisomy 13 (also known as Patau syndrome).
Trisomy means three copies of a chromosome in each body cell instead of the typical two.
"This is the first universal, noninvasive test for Down’s. It could be the first step in putting an end to invasive testing procedures like amniocentesis and chorionic villus sampling," Quake said in a telephone interview.
The findings are published online in the Proceedings of the National Academy of Sciences. #