Down’s Syndrome(DS) is a condition in which extra genetic material causes delays in the way a child develops, and often leads to mental retardation. It affects 1 in every 800 babies born.
The symptoms of Down’s Syndrome varies from child to child. Some children with Down’s Syndrome may need allot of medical attention, others with Down’s Syndrome lead healthy and independent lives.
Normally, at the time of the child’s’ conception, he/she will inherit genetic information from it’s mother and father, which consists of 46 chromosomes, 23 from the mother, and 23 from the father. In most cases of DS, a child will inherit and extra chromosome for a total of 47. This is what causes the physical and cognitive delays associated with Down’s Syndrome. It is recommended that women at the ages of 35 and over, be tested for DS because they have a greater risk of having a child with Down’s Syndrome.
Children with DS also share certain facial features such as a flat facial profile, an upward slant to the eyes, small ears, a crease across the center of the palms, and an enlarged tongue. A doctor can usually tell if a newborn has DS by giving a physical exam.
Low muscle tone, and loose joints are also a characteristic of Down’s Syndrome, along with being “floppy”. This can, and often does improve in time.
Down’s Syndrome can not be prevented, but it can be detected before a child is born, and the health problems that go along with DS can be treated.
A new non-invasive test that examines fetal DNA can pick up genetic abnormalities such as Down’s Syndrome, researchers said on Friday.
This new diagnostic tool developed by the US company Ravgen poses no threat to the mother or fetus, unlike more intrusive tests that may raise the risk of miscarriage.
It uses fetal DNA extracted from blood samples taken from the mother to screen for chromosomal abnormalities; 60 pregnant women reported that the test produced promising results.
“Right now, in the market, there is no test available that can reliably do what we do in this study which is, without needing any invasive procedure, to determine whether a baby has abnormalities or not,” said Ravinder Dhallan. lead author of the study, and the head of Ravgen.
The blood test correctly identified Down’s Syndrome in two different cases. It also produced a false positive, and a false negative.
Dhallan said the test can look for abnormalities in any chromosome or gene disorders.
Recently the American College of Obstetricians and Gynecologists has recommended that all women be given the option of having genetic testing.
The standard tests that are used to detect DS include CVS(chorionic villus sampling), and amniocentesis, which is performed in the first 13 weeks of pregnancy. It analyzes placenta cells to detect any abnormalities.
Amniocentesis is done at about 16 weeks and involves inserting a needle to withdraw a small amount of amneotic fluid.
The new test detects genetic abnormalities in the fetus by looking at single nucleotide polymorphisms, or SNPS, which are tiny variations in DNA.
Dhallan says that he sees the test being used along with other tests, and the results are ready in two to four days. Doctors say the results are encouraging, but larger studies need to be done.
“Dhallan’s test is promising and opens a new era in parental diagnosis but to be optimally used as a routine prenatal screening or diagnostic test, their findings need to be replicated in a large scale multi-center setting, ” said Alexandria Benachi, of the hospital Nekar-Enfants Melads in Paris, and Jean-Marc Costa, of the American Hospital of Paris.
Sources: (http://www.kidshealth.org/parent/medical/genetic/down_syndrome.html), www.kidshealth.org