Genetic Screening
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Chromosomal abnormalities account
for nearly 15% of mid-trimester . Fortunately, there exists for all pregnant women an opportunity for a
comprehensive prenatal evaluation of their fetus for the purpose of determining
genetic and morphologic (structural) normalcy.
Although it is not considered
mandatory or routine, women at risk for fetal problems may avail themselves
of several testing procedures as well as be offered screening procedures . Examples of these procedures include: ; ; fetal blood
sampling; ; high resolution and direct fetal visualization via fetoscopy.
Because some of these tests are invasive it is important for
the patient and her physician to have a clear understanding of what information
is to be ascertained from a particular test, its risks and its limitations.
With these guidelines well defined, the prenatal diagnosis
of fetal abnormalities becomes an important tool in the contemporary care
of pregnancy.
Pre-pregnancy counseling or is very important, and women should
consult their physician or other primary caregiver prior to conception,
or at least very early in the first trimester, so as to determine any
risk factors for genetic diseases; e.g. familial disorders such as cystic
fibrosis, muscular dystrophy, hemophilia, sickle cell anemia, Tay-Sachs
Disease or chromosomal disorders, the most common being or Trisomy 21.
Carrier states can then be detected prior to conception or early in the
pregnancy. Appropriate diagnostic tools may be utilized as described above:
blood sampling, chorionic villus sampling, amniocentesis and high resolution
ultrasound. For families who have been identified at risk for these or
other hereditary diseases, is indicated.
For families not at risk for genetic disorders , certain screening tests
(non-invasive) are available.
The maternal test (now
combined with two other markers-HCG and Estriol) is a screening test primarily
for two particular classes of disorders; (NTD) and
chromosome abnormalities, the most common being or Trisomy
21. If the test should return as positive , either above or
below the limits of the mean, it does not necessarily indicate there is
a problem-only that their might be a higher risk for a problem. The next
procedural step would be to perform a detailed exam, sometimes
called a level 2 scan and possibly an . These
second line tests can better define the health of the fetus within the
limitations of each test.
Genetic testing today, although available now for many years, is on the
cusp of a new frontier-that of very early, embryonic diagnosis via micro-fetal
blood sampling and maternal blood sampling for fetal cells and fetal chromosome
analysis. Early fetal treatment may also be possible through current and
ongoing research in gene manipulation and therapy.
For further, more detailed information on this topic,
please refer to the reference source for this page.
The information in this page is presented in summarised form and has been taken
from the following source(s):
1.
Hygeia Foundation : http://hygeia.org/
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Introduction
