Prenatal Genetic Testing
By Emily Bloch for Your Baby Today
Expectant parents almost always have one thing in common: They're hungry for
information about the health of their baby. Here is a list on tests that can
detect the presence of birth defects and other abnormalities:
Maternal serum screening
What is it? A simple blood test that screens for levels of
alpha-fetoprotein (AFP), as well as the hormones estriol and hcG
What can it detect? Indications of the risk of your baby having a brain,
spinal, or abdominal-wall defect, or Down syndrome
Are there any risks? No, though there is a chance of a "false
positive"--a result that says your risk is high, when it really isn't. This chance
would be ruled out by one of the diagnostic tests described below
Who gets it? All pregnant women
When? 15 to 18 weeks; results are usually available within 1
to 2 weeks after your appointment
Ultrasound
What is it? A procedure in which a practitioner moves an
instrument--often resembling a wand--across your abdomen or places a small device inside
your vagina, in order to produce an image of your fetus on a video monitor
What can it detect? The age and gender of your fetus, how fast it's
growing, the location of your placenta, if you're carrying twins, and whether your fetus
has a neural-tube defect
Are there any risks? No, though there is a chance of a false positive, as
with maternal serum screening
Who gets it? Women who have abnormal blood- screening results, whose
doctors want to confirm the age of the fetus, or who have any potential problem. Some
doctors offer ultrasound to all pregnant women
When? Depends on the reason for the ultrasound; if it's in
response to an abnormal screening result, usually very soon after those results are in
Amniocentesis
What is it? This is a very accurate diagnostic test, in which a
doctor, guided by an ultrasound, inserts a needle in your abdomen and draws a small sample
of amniotic fluid
What can it detect? Evidence of neural-tube defects, Down syndrome, and
other chromosomal defects; it can also determine the gender of the fetus
Are there any risks? Yes. Side effects include cramping, vaginal bleeding,
and leaking of amniotic fluid. While the chance of something happening to your fetus is
rare, 1 in 200 women has a miscarriage due to this procedure
Who gets it? Women who have a family history of birth defects, who
already have a child with a birth defect, or who are age 35 or older. It is also done to
double-check the screening tests, such as AFP
When? 14 to 18 weeks; it can take 3 weeks for the results
Chorionic villus sampling (CVS)
What is it? Chorionic villi are the tissue that make up the
placenta; since the villi come from the same fertilized egg as the fetus, they share the
same genetic makeup and contain a lot of information about your fetus' health.To obtain cells, your doctor withdraws a small amount of tissue from placenta
by inserting a catheter into your vagina or a needle through your abdomen
What can it detect? Similar chromosomal problems to
amniocentesis
Are there any risks? Yes. The most common risk is miscarriage. One in 100
women has a miscarriage she would not normally have had because of CVS
Who gets it? Women with similar situations as those who get
amniocentesis; the difference is that CVS can be performed up to a month before amnio, so
you can be sure of the status of your pregnancy earlier on
When? 10 to 12 weeks; results are available within 3 weeks
Also see:
First Trimester Doctor Visit
Second Trimester Doctor Visit
Third Trimester Doctor Visit
©Studio One Networks
The content on these pages is provided as general information only and should not be substituted for the advice of your physician.
