A newly developed blood DNA test given to expectant mothers can determine if an unborn baby has Down syndrome or other similar birth defects. Unlike invasive procedures such as the amniocentesis and chorionic villus sampling (CVS), the test poses no risk to the fetus.
Down syndrome occurs when a child has three, rather than two, copies of the 21st chromosome. The condition causes mild to moderate impairment of cognitive ability.Common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. Down syndrome increases the risk for certain medical conditions such as congenital heart defects, respiratory and hearing problems, Alzheimer's disease, childhood leukemia, and thyroid conditions. One in every 733 babies is born with the condition and there are over 400,000 people living with Down syndrome in the United States.
Stanford University bioengineer Stephen Quake, Ph.D., of Stanford University in California led the research team in creating a way to examine small amounts of fetal DNA that circulate in the mother's blood to look for extra chromosomes that trigger Down's syndrome and other similar birth defects. “We sequence millions of molecules from each blood sample and map the DNA back to the chromosome. And then we look to see if any chromosomes are over-represented,” Quake said.
The test requires only a small blood sample from the mother, making it much safer than sticking a needle in the uterus as required by the amniocentesis, or using of CVS, which requires snipping off a small piece of the placenta for analysis. Both invasive procedures carry a risk of causing a miscarriage or birth defects.
The blood test can also be done very early in a pregnancy, as early as five weeks after conception, with results available within a couple of days. With invasive procedures, which are typically done after the 15th week of pregnancy, results can take two to three weeks.
Although Down syndrome is the most commonly occurring chromosomal condition, other dangerous chromosomal conditions exist that can also be detected by the new test. One such condition is Edward syndrome, a condition that is caused by the presence of three, as opposed to two, copies of chromosome 18 in a fetus or infant's cells. The syndrome occurs in about one in 3,000 pregnancies and approximately one in 6,000 live births and has a very low rate of survival due to heart abnormalities, kidney malformations, and other internal organ disorders.
Another condition indicated by the new test is Patau syndrome, in which a patient has an additional chromosome 13. The condition causes numerous physical and mental abnormalities, with the most predominant being heart defects, and kills more than 80 percent of children in infancy. Patau syndrome affects approximately 1 in 12,000 live births.
2 comments:
All these tests are wonderful, knowing what the health may be of your child. However it should be clear to women getting a prenatal diagnosis that in some cases, such as Trisomy, specifically Trisomy 13. There may be added pressure for terminiation or early induction.
These tests do not clearly give you the specifics of each medical abnormmality that may come with trisomyt 13/Patau Sydnrome. Families would still need further testing for those specifics. Ultrasounds will tell some of the expected abnormalities, however, these tests have their flaws also. Each child is unique and will present the trisomy 13 differently. There are many survivors...in fact, MANY long term survivors. You can view them and family support and resources at
Living with trisomy 13
http://www.livingwithtrisomy13.org
My child is 8 yrs. She is a spcecial needs child. She came with many of the medical complications that come with these t13 kids. She is full trisomy 13 and has been fortunate enough to have a medical team of professionals who supported out choice for medical intervention. Unfortunately some families are not given the option of medical intervention once the Label of trisomy 13 is attached to their child. Families should be fully informed on the many aspects of the early dection tests. Getting well informed will help them make the best decisions for the well being of their child.
(typos corrected)
All these tests are wonderful, knowing what the health may be of your child. However it should be clear to women getting a prenatal diagnosis that in some cases, such as Trisomy, specifically Trisomy 13. There may be added pressure for termination or early induction.
These tests do not clearly give you the specifics of each medical abnormality that may come with trisomy 13/Patau Syndrome. Families would still need further testing for those specifics. Ultrasounds will tell some of the expected abnormalities, however, these tests have their flaws also. Each child is unique and will present the trisomy 13 differently. There are many survivors...in fact, MANY long term survivors. You can view them and family support and resources at
Living with trisomy 13
http://www.livingwithtrisomy13.org
My child is 8 yrs. She is a special needs child. She came with many of the medical complications that come with these t13 kids. She is full trisomy 13 and has been fortunate enough to have a medical team of professionals who supported out choice for medical intervention. Unfortunately some families are not given the option of medical intervention once the Label of trisomy 13 is attached to their child. Families should be fully informed on the many aspects of the early detection tests. Getting well informed will help them make the best decisions for the well being of their child.
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