Headlines
As reported by the Journal-Constitution, August 30, 2004.
Prenatal Breakthrough: New Test for Women at Risk Is Less Invasive, But Not as Accurate
By Elvira Viveros
Pregnant women, especially those over 35, often anguish for months over the healthy development of their baby.
Now, a new noninvasive prenatal screening test that detects genetic disorders as early as 11 weeks has given women a reason to breathe — and sleep — a bit easier.
The American College of Obstetricians and Gynecologists this summer said that first-trimester screenings utilizing ultrasound and a blood test should be offered as an option for women who are at risk of a genetic disorder. /p>
With an 85 percent success rate in detecting a chromosomal disorder, it is not as accurate as amniocentesis, the most widely used prenatal screening test, which has a accuracy rate of between 99.4 percent and 100 percent. It doesn't even have a formal name.
Yet many are saying the new method is a huge breakthrough.
It provides a picture of prenatal health without the risks of a probing needle that is used to extract fluid from the uterus during diagnostic tests such an amniocentesis, which is done in the second trimester or extracting tissue from the placenta in a chorionic villus sampling (CVS), done in the first trimester.
The first-trimester screening consists of a blood test and an ultrasound exam, called nuchal translucency screening, which measures the thickness of the back of the fetus' neck.
If there is an abnormality of thickness of the nuchal translucency, then the result is said to be a positive-risk.
"For me it was a no brainer," said Atlanta resident Sue Robinson, 40. Robinson, who is pregnant and has a 7-month old son, had an earlier miscarriage.
"I was a little nervous about the more invasive tests and I didn't want to disturb anything going on during my pregnancy," she said. Her results from the first-trimester screening came back normal and she held off on the amniocentesis.
According to the Centers for Disease Control and Prevention, birth rates in 2002 for women older than 35 were at their highest in three decades at 13 percent.
As women age, their risk of giving birth to a Down syndrome baby increases. At age 35, for instance, a woman has a one in 400 chance of having a Down syndrome baby. That increase to a one in 110 chance by age 40, according to the National Down Syndrome Society.
Because one out of 800 babies are born with Down syndrome regardless of the mother's age, Dr. Michael Randell, an obstetrician and gynecologist at Northside Hospital in Atlanta, said it is always wise for a woman to be screened in order to evaluate her risk.
"We tell women that this first-trimester screening is not an alternative to amniocentesis but an option to learn sooner what the odds are," said Randell.
Until recently, blood tests called quad tests were given in the second trimester at 15 weeks in order to calculate the risk of having a baby with a genetic disorder such Down syndrome or trisomy 18, which is characterized by heart disorders and physical malformations.
Doctors agree that if the fetus is found to be affected earlier in the pregnancy, it provides women greater privacy if they elect to terminate the pregnancy.
"The first-trimester screening test, helps doctors avoid basing medical decisions on a woman's age alone with no risk to the mother or fetus," said Randell.
He said if the results are positive a woman can decide if she wants to take a diagnostic test that give definitive results such as a CVS or amniocentesis, at 15 to 20 weeks. Both procedures are invasive and have a .5 percent to 1percent chance of miscarriage.
Janice Lee-Hightower of Atlanta, 37, who is pregnant, said knowing earlier put her mind at ease.
"It gave me and my husband comforting results, and for me, an amniocentesis was not something I was looking forward to," she said. She had a miscarriage before her current pregnancy and was unwilling to take the slight risk that is associated with more invasive tests, she said.
Dr. James F.X. Egan, professor of Obstetrics and Gynecology at the University of Connecticut co-authored a study on noninvasive screening methods and found that new first-trimester test can be just as accurate as second-trimester tests.
As more research is available to the public, the tests will be offered with more confidence.
"We know that as noninvasive tests get better, fewer people are told that they are at risk, meaning fewer women choose amniocentesis," said Egan.
Jode Asher, genetic counselor at Emory University, said that although insurance companies don't cover the cost of the test, that may run about $350, growing number of women who might be at risk are asking for the tests.
"Patients I work with like the idea of knowing what to expect," said Asher.
"One of the minuses is that we are going to occasionally miss a Down syndrome risk." She said that it is important that women understand that this is not an alternative to an amniocentesis but really a risk assessment of their chances of having a baby with a genetic disorder.
A Guide for Expectant Parents
Test: First-trimester screening
What: Consists of a blood test and an ultrasound exam, which measures the thickness of the back of the fetus' neck
When: Between 10 and 14 weeks
Pros: Reduces maternal anxiety earlier in the pregnancy and poses no risk to mother and fetus
Cons: Might miss 15 percent of cases with Down syndrome or trisomy 18
Test: Chorionic villus sampling (CVS)
What: Detects chromosomal problems like Down syndrome, cystic fibrosis, and sickle cell disease by removing a tiny piece of tissue from the placenta
When: 10 to 12 weeks
Pros: Early test relieves anxiety; 95 percent accuracy rate
Cons: Invasive test that carries a slight risk of miscarriage of 1 in 200 to 1 in 400
Test: Quad test
What: Detects Down syndrome, trisomy 18 and neural tube defects
When: Between 15 and 20 weeks
Pros: Noninvasive blood test
Cons: Detects only about 60 percent of cases of Down syndrome
Test: Amniocentesis
What: Test that detects most chromosomal disorders such as Down syndrome, trisomy 18 and spina bifida by inserting a needle through the abdomen to remove fluid from the uterus
When: Between 15 and 20 weeks
Pros: Accuracy rate of between 99.4 percent and 100 percent
Cons: Risk of miscarriage is 1 in 200 to 1 in 400
Test: Level 2 Ultrasound
What: Targeted, more powerful ultrasound that scans baby's organs looking for brain abnormalities, problems with stomach, bladder or intestines
When: 18-22 weeks
Pros: Poses no risk to the baby
Cons: Not 100 percent accurate.