21st Century Choices: Down Syndrome Now Detectable During First Trimester From Mother's Blood [VIDEO]
When amniocentesis was first introduced in the 1970s it was designed to take a sample of amniotic fluid from the growing fetus and allow for testing of genetic abnormalities. Down syndrome is the predominant thing tested for and the panel of genetic tests for prenatal babies has grown to over 800 tests such as ones for Tay Sachs, hemophilia and cystic fibrosis. The procedure is usually performed between the 11th and 13th week of pregnancy, yet a new technology will give parents a window into their unborn child's health far earlier, forcing decisions about the health of the mother and child to happen sooner after conception.
New Technology
Details of a new genetic test that used the mother's blood, instead of traditional amniocentesis, to determine genetic issues with the fetus have been published in the journal Ultrasound in Obstetrics & Gynecology. The benefit of such a procedure is that it can be performed in the first trimester, giving parents more time to make decisions and it only requires a small amount of blood from the mother. This process is safer than an amniocentesis which requires a needle stick in to the amniotic sac of the baby to collect fluid, which carries the risk of miscarriage.
The technique is made possible because of recent findings that fetal DNA can be detected in the blood of the mother and distinguished from the mothers DNA, as shortly as five weeks post conception. Additionally, next-generation DNA sequencing technologies have recently come to market that can sequence an entire genome fairly quickly and cheaply compared to the years and millions of dollars it cost when the human genome was sequenced a decade ago. The technique can detect the presence of fetal DNA that contains extra chromosomes, and compare them to the mothers DNA. Three sets of some chromosomes are called trisomy, which is abnormal compared to the regular set of two chromosomes humans have, one set from the father and one set from the mother.
Trisomy of chromosome 21 is evidence of Down syndrome and other chromosomal abnormalities can be detected by the new technique as well. Trisomy of chromosome 18 and trisomy 13 can be detected, as well as an extra or missing copy of the sex linked X chromosome. Women have two X chromosomes and men only have one accompanied by a smaller Y chromosome. Any desperate number of X chromosomes can lead to a child that may develop some health problems, or have an indeterminate sex.
While the test currently costs around $50,000, prices for whole genome sequencing is dropping rapidly and many believe that the cost will drop to $1,000 within a few short years.
In the current study, researchers took blood samples for women who were in the high risk category for carrying a child with Down syndrome. The 1005 women in the study had a median age of 37 and were pregnant with only one child. By comparing their blood test to an amniocentesis test for confirmation, they found that all cases of suspected Down syndrome truly had the genetic abnormality. All but one blood test was confirmed, and that was for trisomy 18, another disease. In total the testing showed that their new non-invasive technique had a small false positive rate and matched traditional testing techniques.
Currently women who find out that their baby has trisomy 21 and will be born with Down syndrome have to make a difficult decision whether to keep the child or obtain an abortive procedure. About 65 percent of U.S. women presented with the information that her child has Down syndrome decide to terminate their pregnancy. This is a difficult and emotional decision that women and their partners make to weigh the value of life and the responsibility of bringing someone into the world with a known genetic issue that will disadvantage them.
What to do now?
This new technology will allow parents to know if their unborn child has many other genetic problems, in addition to Down syndrome, far earlier than ever before. This is sure to affect the rates of pregnancy termination, as the fetus is smaller and the new testing still sits within the first trimester, when non-medical necessary or advised abortions are legal to carry out in many states. In addition to the ability to perform these tests early in pregnancy, the technology to sequence the entire genome of an unborn child at the early stages of pregnancy open up a Pandora's box of which ethicists will spend entire careers working on.
Parents will able to know what risk their child carries for developing certain cancers. It is entirely within the realm of possibilities that parents may chose not to give birth to a child that they know is predisposed to breast cancer because of faulty BRCA genes. If people such as Angelina Jolie preemptively remove their breasts to prevent breast cancer, would similar logic prevail in preventing a child to be born who is known to be at significant risk for cancer?
Many in the field say that this is unlikely to happen because by the time children become adults and are affected by genetic based diseases, such as the neurodegenerative Huntington's disease which strikes when someone is in their 30's, new treatments may be available to allow people to live long and healthy lives.
Science is advancing far quicker than movies and science fiction had predicted. GATTACA, an all-star thriller follows a non-genetically enhanced man who is living in a world of genetically superior people. At birth he is tested and receives a high likelihood of dying in early age of heart failure, and beats the odds by living a long life, although with much stigma. Now we have the technology to detect fatal genetic issues well before birth. What we are going to do with that information is up to us.
To learn some interesting facts about DNA and genetics, watch the video below from the BBC.
BBC Knowledge Explainer DNA from Territory on Vimeo.
Source: Gil M, Quezada M, Bregant B, Ferraro M, Nicolaides K. Implementation of maternal blood cell-free DNA testing in early screening for aneuploidies. Ultrasound in Obstetrics & Gynecology. 2013.
