Tests for Blood-Sugar Levels
Many doctors test every pregnant woman
for diabetes, usually around the end of the second trimester. Testing
is particularly important if you have a family history of diabetes.
Blood tests used to diagnose diabetes are a fasting blood-sugar and
glucose-tolerance test (GTT).
For a fasting blood-sugar test,
you eat your normal meal the evening before the test. In the morning,
before eating anything, you go to the lab and have a blood test done. A
normal result indicates diabetes is unlikely. An abnormal result (a
high level of sugar in the blood) needs further study.
Further study involves the glucose-tolerance test (GTT).
You must fast after dinner the night before this test. In the morning
at the lab, you are given a solution with a measured amount of sugar in
it to drink. It is similar to a bottle of soda pop but doesn’t taste as
good. After you drink the solution, blood is drawn at predetermined
intervals, usually at 30 minutes, 1 hour and 2 hours and sometimes even
3 hours. Drawing the blood at intervals gives an indication of how your
body handles sugar. If you need treatment, your healthcare provider can
devise a plan for you.
Nuchal Translucency Screening
Nuchal translucency screening is
a test to help healthcare providers and pregnant women find out if a
fetus has Down syndrome. Results are available in the first trimester.
A detailed ultrasound allows the doctor
to measure the space behind baby’s neck. When combined with blood
tests, the results of these two tests (ultra-sound and blood test) can be used to predict a woman’s risk of having a baby with Down syndrome.
Because results are available early, a
couple may make earlier decisions regarding the pregnancy, if they
choose to do so. When this test is done between 10 and 16 weeks of
pregnancy, it accurately detects Down syndrome more than
95% of the time. In fact, it is the single-most powerful screening tool
for Down syndrome. One study showed that doing this test in women with
a higher risk of having a baby with Down syndrome increased the rate of
detection of Down syndrome from 60 to 80%.
Ultrasound is the standard test used to
diagnose birth defects and other fetal anomalies. It is usually the
first test used, but there are some limitations to ultrasound
evaluation. If a pregnancy involves an obese mother-to-be, decreased
fluid around the baby (oligohydramnios) or an abnormal fetal position,
ultrasound may not reveal problems. In addition, its optimal use is in
midpregnancy, so earlier or later use of the test may not be as helpful.
Another test in use has fewer
limitations—fetal MRI. Fetal MRI (magnetic resonance imaging) provides
excellent tissue contrast and is not limited by maternal obesity or
fetal position. This test is most helpful when findings from ultrasound
are unclear or cannot be seen clearly.
Unlike X-ray and CT scans, MRI does not
use ionizing radiation. Several studies have demonstrated the safety of
MRI on human embryos and fetuses. To be cautious, MRI is still not
advised during the first trimester. The test is used to identify
conjoined twins, a diaphragmatic hernia, oligohydramnios, various large
tumors, diagnosing fetuses with brain abnormalities and masses in the
It’s important to note
ultrasound is more widely available and less expensive than MRI.
Ultrasound is still the first choice for diagnosing fetal problems.
However, MRI can be helpful in special situations, as mentioned above.
Instant Risk Assessment (IRA)
A screening test for Down syndrome, called IRA
(Instant Risk Assessment), offers women faster results at an earlier
stage in pregnancy and has a 91% accuracy rate. IRA has two parts, a
blood test and an ultrasound. Women receive a collection kit from a
provider or hospital.
The mother-to-be pricks her finger and
marks a card in the kit with her blood, which is sent to an IRA lab for
analysis. It is tested for levels of HCG (human chorionic gonadotropin)
and a substance called pregnancy-associated plasma protein A.
Both are produced by the placenta and help maintain the uterine lining,
but elevated levels have been associated with Down syndrome.
The second part of the test, the
ultrasound, is a nuchal translucency exam, in which an ultrasound
measures the space on the back of the baby’s neck. The more space in this area, the higher the chance that baby has Down syndrome. Your doctor can schedule the ultrasound.