Family Forum / Pregnancy / Pregnancy / June 2005

someone will know better than me, but just anecdotally, people who have had
a 'bad' result that i have heard have been looking at something like 1 in 8,
but mine have always been 1 in 300 or something.

for me, it started at say 1 in 300 jus tb/c of my age then after the test it
reduce to say 1 in 500 or something like that (i cant remember exact
figures)

i found the figures easy to interpret

hth

    That's completely up to you.  There isn't any arbitrary
line.  All this test will tell you is that statistically, there
is a 1 in X chance that your baby has Downs Syndrome.  Based
on that information, you will decide whether you want to do
further testing (e.g., amnio, detailed ultrasound, etc.).  The
triple screen only tells you if you're at increased risk.  It
does not tell you whether your baby will have DS.  If you want
to have a definitive diagnosis, amnio will get that for you,
but at an increased risk of miscarriage due to the procedure.
Detailed ultrasound can get you some more information on whether
the baby has any visible soft markers for DS, so you'd know a
little more than with just the triple screen and little additional
risk, but you would not have a definitive diagnosis.  To help
weigh the risks and benefits, you need to have some ideas about
what you'd do differently if your baby did turn out to have DS.
Would you terminate?  Would you do your prenatal care differently?
Would you change something about your birth plans?  The answers
to those questions tell you whether you might want to take the
risk of having an amnio.  If your triple screen comes back saying
there's a 1 in 50 chance of DS, then maybe you're willing to
take more risks to find out for sure than if it says there's a
1 in 800 chance.  But really, only you can decide where your
risk preferences are.

Best wishes,
Ericka

They'll prob. tell you it's "screen positive" if the risk is more than 1/200
(for the statistically-challenged, this means the lower number is less than
200). :) Why is this number "screen positive"  you ask?  Simply because
that's the commonly quoted risk of miscarriage resulting from amniocentesis.
Since amnio is the test that gives you a definitive Down Syndrome answer but
has a miscarriage risk, most Dr's won't offer it unless your starting risk
is equal to or greater than losing the pregnancy due to the test.  That
sentence was convoluted:  basically, if there is a greater chance of a test
hurting you than "helping" you, most Dr's won't do the test.  Keep in mind
this equation assumes equal importance between a diagnosis of Down Syndrome
and a miscarriage.
If your risk is right around 1/200 (or higher for that matter), you might
feel comfortable with a level II ultrasound to look for any further
indications before deciding about amnio.  If you are a person that needs
definitive answers, the only way you'll get that is amnio with the
associated risks.

Keep in mind that the triple screen has a high "false positive" rate
(usually quoted around 90% IIRC)  This means that 90% of women who have a
risk number of 1/200 or higher do _not_ have a baby with a chromosomal
problem.  The test is meant to "catch" as many true positives as possible,
so a lot of false positives are caught as well.

Good luck!
Amy

It depends on your family history and your age... I think and some
other factors.

I have a family history of spina bifida.  I was 1 in 100 before I had
the test.  With #1, the result was 1 in 3500 (I think) and with #2 it
was similar.  

Your doctor will tell you if there is any cause for concern, but when
I heard that it was 1 in a number that was in the thousands, I knew
there was little to worry about.

FYI, if you get a "bad" result, it doesn't mean that there is
something wrong with the baby.  False positives are know in these
tests.  Further testing will rule out if there are any real problems.

--
Daye
Mommy to DD3 and DS1