PRENATAL TESTING
Certain prenatal tests are standard screens for the health of the
mother and the developing fetus. These include testing for sexually transmitted diseases
such as syphilis, hepatitis B, Gonorrhea, and Chlamydia. Although testing for AIDS
isn’t considered standard, our office policy recommends testing all mothers for
infection due to the fact that there is now treatment that can be given to the mother to
significantly decrease the transmission of the infection to the fetus. Furthermore, if a
policy is in place to screen all patients for the disease, insurance is less likely to
consider it a red flag. Other initial tests include screening for anemia, RH disease,
chronic infection, low platelets, and Rubella immunity. A urine culture is usually
obtained by the second visit to screen for asymptomatic urinary tract infection.
Second trimester screening is limited to the triple-screen AFP, a test
developed for the detection of neural-tube defects (such as anencephaly and spina bifida)
and common genetic syndromes, such as trisomy 21, (Down’s Syndrome) trisomy 18, and
trisomy 13. This screen is usually run between 15-19 weeks gestation, and if it comes back
abnormal, further testing is recommended to rule-out the presence of these problems.
Further testing includes genetic consultation, a Level II ultrasound, and possibly an
amniocentesis. A Level II ultrasound is a more in-depth sonogram looking at all of the
organ systems of the fetus as well as to assess growth, amniotic fluid, the placenta,
uterus, ovaries, and maternal kidneys. An amniocentesis is a test where fluid is withdrawn
and fetal cells are cultured for later determination of genetic abnormalities as well as
certain metabolic diseases of the fetus. It is important to remember that the
triple-screen AFP is just a screening test designed to determine risk. If it comes back
abnormal, it does not mean that there definitely is a problem. In fact, after all of the
evaluation processes are complete, the results frequently confirm a normal fetus. One
needs to keep this in mind while undergoing an evaluation for an abnormal screening result
to reduce the inherent anxiety that the abnormal screening test produces.
Beginning in the last trimester, the mother is screened for gestational
diabetes with a one-hour glucose tolerance test. If this test returns abnormal, further
testing is done with 3-hour glucose tolerance test. This test will confirm the presence or
absence of diabetes. In the last month of pregnancy the mother is cultured for Group B
B-hemolytic Streptococcus. If this culture comes back positive, the mother is considered a
carrier for this bacteria, and will be treated in labor with an antibiotic to reduce the
risk of infection to the newborn. Carrier status is often transient therefore culturing is
done the during the last month of pregnancy.
Other tests can also be run during the pregnancy, depending on a
patient’s ethnicity or race. Examples of these kinds of test include sickle-cell
screening in patients of Afro-American descent or Tay-Sachs screening for those patients
who are Jewish. Naturally, if a patient has a chronic ailment, further testing will be
specific to that problem, as in the case of a patient with chronic kidney disease or
hypertension. All of the prenatal tests run through this office, although recommended, are
not mandatory. The patient reserves the right to refuse all testing. Please keep in mind
however, that these tests are there for the detection of problems that could influence the
outcome of the pregnancy. We encourage you to discuss any questions or concerns about
prenatal testing with your provider.
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