Down Syndrome Tests Risky for All Babies, Study Shows
September 19, 2008 - 4:49 AMFor every three babies found through prenatal testing to have Down syndrome, two babies without the condition are lost through miscarriage as a result of the test, a new study estimates.
About 660 babies each year in England and Wales are found through testing to have Down syndrome, say the authors. In most cases, parents choose to have an abortion.
An estimated further 400 babies who are tested but found not to have the condition die as a result of a miscarriage, say Prof. Sue Buckley and Frank Buckley of Down Syndrome Education International (DownsEd), a charity that opposes genetic screening and the abortion of babies who test positive.
The American College of Obstetricians and Gynecologists recommends that all pregnant women be offered prenatal screening before 20 weeks’ gestation, preferably in the first trimester. Britain’s health authorities have made similar recommendations.
Prenatal screening generally involves ultrasound or blood tests, and women who screen “positive” – those whose babies are estimated to be at increased risk of having Down syndrome – may then decide to have what is considered to be a more accurate diagnostic test.
These are usually amniocentesis, the collection by needle and testing of amniotic fluid from the womb; or a procedure called Chorionic villus sampling (CVS), in which tissue from the placenta is taken and tested.
The DownsEd report says that, according to the best available evidence, the risk of pregnancy loss resulting from amniocentesis is one percent (one child in 100) and in the case of CVS, two percent (one child in 50).
But it also notes other factors, such as the level of experience of those carrying out the tests: “Studies have observed loss rates following amniocentesis that are 6 to 8 times higher among less experienced practitioners than among experienced practitioners.”
Moreover, the study estimates that 95 percent of “positive” screens (6,660 out of 7,000) actually are wrong, meaning that a far higher number of women go on to have the invasive – and potentially risky – diagnostic tests than necessary.
The authors say they “do not consider a diagnosis of Down syndrome to be a sufficient reason to justify termination and so disagree with the basic premise for prenatal screening for Down syndrome. Harming babies who do not have Down syndrome in the process seems to us unjustifiable.”
As a result of its findings, DownsEd wrote this week to British Prime Minister Gordon Brown, calling for a review of “the purpose, performance, safety and ethical justification” for Down syndrome prenatal screening.
Sue Buckley, the charity’s director of science and research and emeritus professor of developmental disability at the University of Portsmouth, also asked for a review of research priorities and policies and services for people with Down syndrome.
She called for a recognition of the fact that increasing numbers of people with Down syndrome are being born, and that they are living longer.
“Over the past 50 years, better treatment and preventive healthcare has helped to improve life expectancy for people with Down syndrome from around 12 years to around 60 years.”
But another British charity, the Down’s Syndrome Association, was critical of the research.
“There has never been any dispute that current diagnostic techniques have associated risk and that women need to be better and fully informed of these risks,” said the organization’s research advisor and professor of developmental disabilities in childhood at the University of Edinburgh, Jennifer Wishart.
“The ‘two for three’ emphasis – that two healthy babies are lost for every three babies with Down’s syndrome prenatally detected – simply muddies the waters,” she said.
‘Truly informed decisions’
The issue of Down syndrome has been spotlighted in recent weeks as a result of the selection of Alaska Gov. Sarah Palin as the Republican vice presidential candidate.
Palin’s son, Trig, born in April, has Down syndrome. The Palins learned of his condition through an amniocentesis test at 13 weeks and chose to continue with the pregnancy.
In her acceptance speech at the Republican National Convention last month, Palin told families with special-needs children, “I pledge to you that if we are elected, you will have a friend and advocate in the White House.”
According to the National Down Syndrome Society in the U.S., one in every 733 live births is a child with Down syndrome – some 5,000 births each year in the U.S. alone. Today, more than 400,000 people in the U.S. have Down syndrome, it says.
The NDSS’s position on screening is that it should be available to all pregnant women who want it, but that the decision on having the screening or not should be solely that of the mother.
“All expectant parents should be informed as to the purpose of the various screening and diagnostic prenatal tests and given information on the risks, limitations and expense of the tests,” the society says.
“All women, regardless of age, reproductive history or disability status, must be given the absolute right to continue a pregnancy after prenatal diagnosis. They should never be subjected to unwanted pressure from health care professionals or others concerning this decision.”
In Australia, the Down Syndrome Association of New South Wales reacted to the interest aroused by Palin’s nomination to launch a new information campaign that “aims to ensure that pregnant women who receive a diagnosis of Down syndrome have access to complete, accurate and up-to-date information on what it means to have Down syndrome and to raise a child with the condition.”
The association’s acting executive officer, Jill O’Connor, said from Sydney Friday that it shares the DownsEd authors’ concerns that women, if they are to make “truly informed decisions,” need to be much better informed about screening, tests, the risks entailed, and “the potential impact of Down syndrome on an individual and on his family.”
She said newer, non-invasive diagnostic tests currently in development could be expected to reduce the loss of unaffected babies in the future, but she also noted that “termination of an affected pregnancy is not without long term consequences for parents and other family members.”
Although the association says it “takes neither a pro-life nor a pro-choice stand,” O’Connor said in an earlier statement that women who receive a Down syndrome diagnosis are often expected to make a decision on whether or not to continue the pregnancy “while still in shock and in a position of having very little understanding of what it is really like to live with a condition such as Down syndrome.”