Prenatal Testing

[Guest guest]

Hi,

I think once again we have dealt successfullywith the touchy question of

family planning on the list. Of course it raises emotions, it usually does

even if you don't have a genetic disease running in the family. Thanks to

all for insightful and mature postings.

By coincidence I saw this article today, although there is nothing new in

it, I'll file it for future use.

Peace

Torsten, dad of Fiona 5wcf

e-mail: torstenkrafft@...

The Washington Times

March 31, 2002, Sunday, Final Edition

HEADLINE: FACING PRENATAL TESTS;

Screening for problems carries risks to weigh against benefits

BYLINE: By Goldberg Goff, THE WASHINGTON TIMES

BODY:

From the time the pregnancy test turns positive, a pregnant woman

receiving

good prenatal care is bombarded with a menu of tests. AFP? CVS?

Amniocentesis?

Ultrasound? If which tests to take seems confusing, figuring out what the

tests

can and cannot tell you is an additional maze to navigate. " People need to

understand what is available, " says Vivian Weinblatt, a genetic counselor

in

Philadelphia and past president of the National Society of Genetic

Counselors.

" They need to understand what prenatal testing will tell them and then

decide

whether that is valuable information. We can't tell if a baby is perfect;

we are

not smart enough. "

Diagnostic prenatal testing can find many conditions - Down syndrome,

spina

bifida and other chromosomal abnormalities, for instance. Other tests,

based on

a woman's age and other factors, can tell whether she is at a statistically

higher risk than others in her age group for carrying a child with a

particular

condition. Those tests are called screening tests, and many patients are

not

aware of the difference between the two, Ms. Weinblatt says.

One common screening test is the triple screen. Blood is drawn between

the

15th and 20th week of the pregnancy, and levels of the chemicals

alpha-fetoprotein (AFP), unconjugated estriol and human chorionic

gonadotropin

(HCG) are measured. By looking at the levels of these chemicals, doctors

can

tell if a woman is at increased risk of carrying a child with conditions

such as

Down syndrome or spina bifida.

If the results come back abnormal, doctors usually recommend further

testing,

such as a more in-depth ultrasound or amniocentesis, in which a small

amount of

amniotic fluid is drawn and analyzed for more definitive results.

However, expectant mothers should remember that many abnormal test

results

occur because of incorrect information supplied for the formula to

calculate the

result.

About 10 percent of women who take the triple screen will have abnormal

results. Upon further testing, about 2 percent will be found to have a baby

with

defects, according to March of Dimes data.

It is important to remember that screening tests are looking for whether

the

odds are increased, Ms. Weinblatt says. They do not diagnose a condition.

" Even if you have a positive screen, the baby is probably normal, " she

says.

" A test like that can tell you your risk for Down syndrome, such as 1 in

200 or

1 in 150. Even if the odds come in at 1 in 5, that leaves you a significant

chance that the baby is OK. "

Still, even knowing the odds are increased can be quite stressful.

Gordon, a 35-year-old Fairfax mother of three, had elevated results in the

triple screen during her first pregnancy five years ago. She and her

husband

worried a lot as they went through an amniocentesis, then worried more as

they

awaited those test results.

" For a whole week, we couldn't talk about it at all, " Mrs. Gordon says.

" A

bunch of my friends have gone through the same thing. I was really scared. "

To the couple's relief, further testing showed a perfectly healthy boy.

" It caused me a lot of worry, " she says, " but I definitely wanted the

tests

done. I'd rather know than not know. "

Many women may opt not to undergo prenatal testing. That is a personal

decision, but they still should be given information about what is

available,

says Dr. Larsen, professor of obstetrics, gynecology and genetics at

Washington University Medical Center.

" I call it making an offer, " Dr. Larsen says. " The standard now in this

country is if a woman is going to be 35 years old at the time of delivery,

then

it is standard to make her an offer of testing. She may then choose CVS

(chorionic villus sampling) or amniocentesis, or she may choose to do

nothing or

do only a less invasive screening such as ultrasound . The vast, vast

majority

of women do something, at least an ultrasound. If it is done timely, it

will

pick up a large number of problems. "

Age 35 is considered the gold standard in the United States because a

woman's

chances of carrying a child with a chromosomal defect increase with age.

For

example, a woman younger than 30 has a risk of less than 1 in 1,000 of

conceiving a child with Down syndrome. A woman age 35 has a risk of 1 in

400. By

age 40, that risk is 1 in 105, according to the National Institutes of

Health.

Many women already in a higher-risk group because of age will opt to

bypass

screening testing and go right to diagnostic testing, Dr. Larsen says.

Ultrasound, in which high-frequency sound waves form images of the baby

on a

video monitor, can measure a baby's growth, evaluate movement, examine for

malformations, even determine the baby's sex.

More invasive diagnostic tests include CVS and amniocentesis.

In CVS testing, a small sample of placental tissue (chorionic villi) is

taken

between 10 and 12 weeks and analyzed for chromosomal defects. Ultrasound

helps

determine the location of the fetus and the placenta; then a thin plastic

tube

is inserted either through the abdomen or through the vagina to obtain the

sample. There is a risk of infection or miscarriage after the procedure,

says

Dr. Alfred Khoury, director of maternal-fetal medicine at Inova Fairfax

Hospital.

The advantage to CVS testing is that it is done in the first trimester,

Dr.

Khoury says. Because CVS has a miscarriage rate of 1 in 150, Dr. Khoury

often

encourages his patients who opt for testing to go with amniocentesis, which

is

done later (at about 16 weeks) but can provide more information and carries

a

slightly lower risk (about 1 in 200) of miscarriage.

Dr. Khoury says women need to be aware of the risks in either procedure.

Amniocentesis, performed between 16 and 18 weeks, is performed by

inserting a

thin needle into the uterus via the woman's abdominal area. A small amount

of

amniotic fluid is withdrawn and analyzed.

" I don't recommend testing such as amnio for all women over 35, " he says.

" I

recommend they be educated about the risks. There is a 1 in 200 chance of

miscarriage with an amniocentesis. That is nothing to sneeze at. We are

great

consumers of technology but don't always think about the consequences. "

Risks aside, amniocentesis can tell you a lot, Dr. Khoury says. If a

woman

comes in with a high AFP result (indicating spina bifida), the test can

definitively tell if the baby has that condition. The test can count the

number

of chromosomes (which can definitively tell Down syndrome and several other

chromosomal abnormalities). If there is a family history of such conditions

as

sickle cell anemia, Tay Sachs disease or cystic fibrosis, doctors can do

special

testing to look for those disorders, as well.

" I never say, 'Everything is fine,' " Dr. Khoury says. " If the chromosomes

are

normal, I say they are normal. If the exam shows no abnormalities, I say

there

are no abnormalities. What people need to understand is that for all our

knowledge, we are still very ignorant. "

The future of testing

Better first-trimester screening is available and eventually may replace

some

later screening tests, doctors say.

They are now able to combine a certain ultrasound measurement (called a

nuchal translucency) and blood tests in the first trimester to pick up

cases of

Down syndrome with 90 percent accuracy and a false positive rate of 5

percent,

Dr. Khoury says.

In the nuchal translucency test, which is done between 11 and 13 weeks,

ultrasound is used to measure precisely the amount of fluid in a small

space

behind the baby's neck. If a baby has a chromosomal disorder, the amount of

fluid may be increased. The ultrasound result is combined with blood tests

that

measure pregnancy-associated plasma protein (Papp-A) and the chemical

free-beta

HCG.

The nuchal translucency and blood work combine to make a screening test.

It

measures a woman's statistical chances of having a baby with chromosomal

abnormalities, Dr. Khoury says. If the results come back as suspicious, the

woman will be referred for CVS or amniocentesis for more definitive

results.

However, the high accuracy rate of the nuchal translucency means that

fewer

women will have to undergo the risker and more invasive tests, Ms.

Weinblatt

says.

" There is a lot of potential to first-trimester screening, " she says. " I

really do think there is a huge benefit to doing these tests early,

especially

for those patients who can be satisfied with less than 99.9 percent

accuracy.

For patients who have tried a long time to get pregnant, they may be more

inclined to find a less invasive way to test and decrease their chance of

miscarriage. "

Some clinics have taken the nuchal translucency a step farther. The

integrated test, which has been tested and popularized in England, combines

the

nuchal translucency with quadruple-screen results (AFP, estriol, HCG and

the

protein dimeric inhibin-A) in the second trimester. The combined data can

detect

the likelihood of Down syndrome 85 percent of the time with only a 1

percent

false positive rate, says Dr. Wald, a British researcher who wrote

a

study published in the New England Journal of Medicine in 1999.

In the study, Dr. Wald looked at the blood work and nuchal translucencies

of

nearly 100,000 women.

The current false-positive rate for the triple screen alone is 5 percent,

Dr.

Wald points out in his study. He is referring to the rate to determine the

risk

for Down syndrome specifically.

Integrated testing ideally will reduce the number of amniocentesis

referalls,

says Dr. Arthur Zebelman, director of clinical operations for Seattle's

Dynacare

laboratories, one of the companies that does integrated testing in the

United

States.

" The most frustrating and scary thing about current screening procedures

is

that the majority of women referred for further testing do not, in fact,

have a

Down syndrome child, " Dr. Zebelman says.

" I would be hard-pressed to say there is a tremendous economic benefit to

integrated testing, but if you can put a cost on concern of expectant

parents,

then that is significant, " he says. " A 1 percent rate of false positives is

a

lot less than 5 percent. There is some risk of miscarriage with

amniocentesis

and CVS, so a lot of couples want to avoid having them. "

+++++

YOU SHOULD CONSIDER TESTING:

* The mother was exposed to a harmful chemical agent during pregnancy, as

in

chemotherapy.

* Maternal screening tests produced abnormal results.

Things to think about:

Discussing these questions with a doctor or genetic counselor can be

helpful.

* How accurate are the test results?

* How often does my doctor perform the procedure?

* How concerned am I about the risk of miscarriage?

* Will this information change the way I will prepare for the birth of my

baby?

* If a problem is discovered, what are my options?

The ABCs of prenatal testing

Here is a look at some of the most common prenatal tests:

* Ultrasound

What is it? High-frequency sound waves are used to create pictures of

what is

going on inside the body.

What does it test for? It can reveal major structural abnormalities,

including congenital heart defects.

How is it performed? Gel, which acts as a conductor for sound waves, is

placed on the mother's abdomen. The doctor moves a small device called a

transducer over the abdomen, directing sound waves into the uterus. The

sound

waves reflect off bones and tissue and are converted into black-and-white

images.

How long does it take? About 20 minutes

When is it performed? Ultrasounds can be done at any point of the

pregnancy.

How long does it take to get results? Results can be seen on the screen

immediately.

What are risks? The exam is painless and poses no risks.

Are there any potential side effects? No.

* Amniocentesis

What is it? Samples of amniotic fluid are removed using a needle and

tested

for genetic abnormalities in a lab.

What does it test for? Amniocentesis can detect chromosomal

abnormalities,

such as Down syndrome; genetic disorders, such as cystic fibrosis; and

neural

tube defects, such as spina bifida. It also can determine whether a baby's

lungs

are mature enough to breathe on their own.

How is it performed? An ultrasound is performed first to determine a safe

site for the needle to enter. A long, hollow needle is inserted into the

uterus.

A small amount of amniotic fluid is taken from the amniotic sac, which

surrounds

the baby.

How long does it take? About half an hour.

When is it performed? Around 16 weeks gestation.

How long does it take to get results? About two weeks.

What are the risks? There is a chance of infection or miscarriage (about

1 in

200).

Are there any potential side effects? There is a chance the mother may

experience cramping, fluid leakage or minor irritation around the entry

site.

* Chorionic villus sampling (CVS)

What is it? Samples of the cells that line the placenta, known as

chorionic

villi, are removed and tested for genetic abnormalities.

What does it test for? CVS can detect chromosomal abnormalities, such as

Down

syndrome, and genetic disorders, such as cystic fibrosis. Because no

amniotic

fluid is removed, it cannot test for neural tube defects such as spina

bifida.

How is it performed? Guided by ultrasound, the doctor inserts a thin

needle

through the abdominal wall into the chorionic villi. A small sample of

cells is

then removed. The doctor alternately can get the cells by placing the tube

through the woman's cervix.

How long does the procedure take? About 45 minutes

When is it performed? CVS typically is done between nine and 12 weeks

gestation.

How long does it take to get results? Preliminary results usually come in

two

days; final results may take one week.

What are the risks? The risk of miscarriage because of CVS is about 1 in

150.

Are there any other potential side effects? The woman may experience

infection, bleeding, cramping, fever or chills. Some studies have shown a

possible relationship between CVS and limb malformation in the fetus.

* Maternal blood screening

What is it? A blood test that measures levels of three substances in a

woman's blood: alpha-fetoprotein (AFP), unconjugated estriol and human

chorionic

gonadotropin (HCG).

What does it test for? The blood work, combined with factors such as a

woman's age, weight, race and pregnancy history, are calculated to

determine

whether a woman is at an increased risk of carrying a baby with a birth

defect.

How is it performed? Blood is drawn from the woman at the doctor's office

or

at a lab.

How long does the procedure take? About 15 minutes.

When is it performed? The test most often is done between 16 and 18 weeks

gestation.

How long does it take to get results? About one week.

What are the risks? A high number of women with abnormal results are

found,

upon further diagnostic testing, to have normal fetuses. Therefore, there

is a

risk of stress to the parents while undergoing more testing.

Are there any potential side effects? No.

+++++

More info:

Books -

* " Which Tests for My Unborn Baby? Ultrasound and Other Prenatal Tests, "

by

Lachlan De Crespigny, Oxford University Press, 1996. This short book

explains

the basics of prenatal testing.

* " What to Expect When You're Expecting, " by Arlene Eisenberg, Sandee E.

Hathaway and Heidi E. Murkoff, Workman Publishing, 1996. This best-selling

general pregnancy book explains the different prenatal tests in an

easy-to-understand format.

* " Mayo Clinic Complete Book of Pregnancy and Baby's First Year, " edited

by

V. , Morrow and Co., 1994. This book, written by Mayo

Clinic doctors, explains general pregnancy information, including tests

about

which expectant mothers should be aware.

Associations -

* March of Dimes, 1275 Mamaroneck Ave., White Plains, NY 10605. Phone:

888/MODIMES. Web site: www.modimes.org. This nonprofit group, which

advocates

prenatal care and prevention of birth defects, has literature and research

information about prenatal testing. Its Web site also features a guide to

understanding the various tests.

Online -

* At the consumer site for the Mayo Clinic (www.mayoclinic.com), visitors

can

find a simple chart about what the different prenatal tests offer, as well

as

advice on what to consider if you are undergoing testing.

* On KidsHealth (www.kidshealth.org), a site sponsored by the Nemours

Foundation, has an easy-to-read guide to prenatal tests.

* The commercial site BabyZone (www.babyzone.com), offers a chart that

defines and explains prenatal testing.

Sources: Mayo Clinic; March of Dimes