Expectant parents almost always have one thing in common: They're hungry for
information about the health of their baby. Here, a chart on tests that can
detect the presence of birth defects and other abnormalities:
| Test |
What is it? |
What can it detect? |
Are there any risks? |
Who gets it? |
When? |
| Maternal serum screening |
A simple blood test that screens for levels of
alpha-fetoprotein (AFP), as well as the hormones estriol and hcG |
Indications of the risk of your baby having a brain,
spinal, or abdominal-wall defect, or Down syndrome |
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 |
All pregnant women |
15 to 18 weeks; results are usually available within 1
to 2 weeks after your appointment |
| Ultrasound |
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 |
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 |
No, though there is a chance of a false positive, as
with maternal serum screening |
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 |
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 |
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 |
Evidence of neural-tube defects, Down syndrome, and
other chromosomal defects; it can also determine the gender of the fetus |
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 |
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 |
14 to 18 weeks; it can take 3 weeks for the results |
| Chorionic villus sampling (CVS) |
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 |
Similar chromosomal problems to
amniocentesis |
Yes. The most common risk is miscarriage. One in 100
women has a miscarriage she would not normally have had because of CVS |
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 |
10 to 12 weeks; results are available within 3 weeks |
