Don’t sleep and wait till NT scan reveral some
aberrations!!!! Because we now know
that foetal DNA and RNA can be
detected in maternal blood as
early as from 5 weeks
of gestation. Do you believe this???
What is new in Methods of prenatal
diagnosis ? Foetal cells
recovered from maternal
blood provide the only source of pure fetal
DNA for NIPT. : Many disorders
have already been successfully diagnosed
or excluded in utero. Statistical value
( Cell free foetal DNA, NT scan, Double
marker, Quadruple tgets, & TIFA, Foetal Echo):-But definitive tets are from
1) chorionic villus sampling
2) amniocentesis & umbilical vein sampling
Is amniocentesis is the most
exploited invasive tets globally in the female population with the aim
to exclude or substantiate A) chromosomal disorders in the fetus , but also B) infections and C) genetic diseases? Ans:-Possibly yes, Doctors are too worried and
insist on this tets to be very sure .As result much such invasive costly
procedure is done daily across the globe. Prenatal diagnosis is the branch of medicine and in particular
of obstetrics that studies and applies the techniques that reveal
the normality or the
presence of disease of various kinds . In the fetus all the techniques of prenatal
diagnosis are performed during pregnancy and may be invasive or less. Among the best
known amniocentesis is the
most exploited technique nowadays
to highlight the possible presence of A) chromosomal disorders
in the fetus , but also B) infections and
C) genetic diseases such as 1) thalassemia
2) cystic fibrosis 3) hemophilia
spina bifida 4) albinism . However the
method of amniocentesis consists of taking an amniotic fluid sample which is then analyzed . Foetal cells
suspended in the withdrawn liquid
allow us to reconstruct the
chromosome map of the fetus and then to confirm or not its normality .
Limitations
of genetic testing :-- Genetic testing:-
However Genetic testing
are not able to recognize the physical or mental
characteristics of the unborn child which are the result of the
interaction between multiple genes and the environment . Amniotic fluid makes possible to
perform other types of analysis more or less complex and it
is also possible to store the amniotic
fluid makes possible to store the amniotic
stem cells.
Chorionic villus sampling :---CVS is similar
to amniocentesis as a principle
but different as a technique is chorionic
villus sampling in which the cells can be put in culture to show their normality but they are cells taken
outside from the gestational chamber
. Both techniques are
invasive techniques but there are also noninvasive techniques. The development of ultrasound
for example has made it possible to develop
some highly sensitive diagnostic techniques, such as the first trimester combined test the quadruple test and lately
the SCA test in the second trimester all based on the
ultrasound measurement of
anatomical and functional
parameters of the fetus and on the results of blood tests. These are all screening tests then they do not give a definite answer but they
have a statistical value that can
direct toward diagnostic
tests.
What
is cffdna test in maternal blood? Recently an extremely
sensitive test for the most common aneuploidies and in particular. Down syndrome
has been proposed to be
performed on maternal blood. This test
is based on the count of
fragments of specific chromosomes in maternal blood although
not belonging to diagnostic tests
but to probabilistic ones this test is
absolutely the most accurate so far available
with values around 99.99% sensitivity and 0.2% false
positives . Also ultrasound
in th second trimester of pregnancy that can
detect any malformation or fetal
abnormality and fetal
echocardiography which analyzes sonographically the fetal
heart not only anatomically but
also from the dynamic functional point
of view may be considered methods of prenatal diagnosis. This
technique cannot identify
genetic diseases.
Role
of Molecular genetics ?? Ans:- The phenomenal
developments in molecular genetics and
technological refinements which have occurred over the past
decades have
revolutionized the area of
prenatal genetics , state of the art care
commences with comprehensive preconceptional counseling .
Conclusion:- Prenatal diagnosis is now feasible from the moment of conception onward
. Imaging techniques have allowed non invasive diagnosis
while minimally invasive techniques concentrate on sampling maternal
blood for fetal cells or markers of feto placental metabolism.
Invasive techniques
have been rapidly expanding and becoming safer comprising
of A) chorionic villus
sampling B) early amniocentesis or C)
midtrimester amniocentesis as well as very early fetoscopy
and umbilical vein sampling Advances in prenatal diagnostic
techniques allow for earlier more rapid and more effective detection of congenital disorders
Recent advances in non invasive detection
methods such as fetal
ultrasound and the
isolation of fetal cells in the
maternal circulation allow the
intrauterine diagnosis of congenital infections and chromosomal and Mendelian disorders as well as
hematologic disorders.
We currently have the potential to diagnose a number of others for which the
opportunity has not yet arisen. If a A) biochemical B) morphologic C) chromosomal or D) genetic:-deoxyribonucleic
acid alternation is known for a specific condition and is likely to be expressed in one of the
fetal tissues or secretions attempt at prenatal diagnosis is reasonable .
Forget
CS /Lap ports!!!! Know what are gene probes???? Development of specific
gene probes
::Diagnosis of inherited disorders
in utero :-- Our ability to
detect the inherited disorders
in utero will continue to
improve both in the number of specific
disorders successfully diagnosed
or excluded and in the increasingly
earlier stages of pregnancy
at which the disorder can be
detected. Non invasive prenatal testing
and non invasive approach
involves analysis of cell
free fetal DNA in maternal
plasma or serum . Another approach
utilizes fetal cells within
the maternal circulation as a source
of fetal DNA.
Advances in instrumentation
have decreased the risk of the
invasive methods of prenatal
diagnosis and improvement in non invasive methods such as maternal serum screening may eliminate the need for invasive procedures altogether
.
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