Antenatal Care: Diagnostic DNA Testing and other Aspects of your Prenatal Care (Guest Post)





Antenatal care (or
prenatal care) is not in any way obligatory but is very important for
your pregnancy. Antenatal care looks at various aspects of your
pregnancy, making you undergo simple tests (or less simple antenatal
DNA tests) and checkups which are aimed at one thing: ensuring the
pregnancy goes as smoothly as possible and informing you of any
likely complications. There is heaps of information to help you even
before you begin your visits, a little breeze online and you can
begin learning how your prenatal care will unfold week after week,
distinguishing between your screening tests and your diagnostic tests
(the latter usually involve direct fetal DNA sampling and actual
analysis of your baby’s DNA)


Ultrasounds
& fetal biometric measurements


Ultrasounds
essentially use high frequency waves which are then turned into the
imaging. Whilst X rays use radiation, ultrasounds do not and are
entirely safe. The first ultrasound is usually carried out at around
20 weeks. Ultrasounds may also be performed earlier to determine
whether there is a multiple pregnancy or the age of the fetus.
Obstetricians can determine the position of the fetus, the sex of the
baby as well as take fetal
biometric measurements
. These measurements
ensure that the baby is the right size and that development is
progressing as normal. Further diagnostic tests may then be required.
These are essentially prenatal DNA tests which determine the child’s
genetic health. The same procedures used to collect fetal DNA samples
for a diagnostic test are also used for antenatal paternity testing/
paternity testing during pregnancy.


A Sigh of relief
Mommies


So we will be looking at
several tests and especially diagnostic tests and how these have
certain risks; these may include injury to the baby, miscarriage or
on a lighter note, some side effects such as fevers or soreness which
you can easily deal with. However, within the field of antenatal
tests a new science has emerged which is called “non invasive
prenatal/antenatal testing”. Basically, instead of getting the
sample of baby DNA from inside your womb, the sample can be collected
from blood – yes, a simple blood draw from the mother will provide
a sample which contains a mix of her DNA and that of her baby. The
laboratory extraction process for this DNA test is more complex than
that for procedures like amniocentesis and would be too much to go
into for such an article. What you need to know if that whilst
invasive tests carry risks, non invasive tests are absolutely
“riskless” and many laboratories have focused on developing and
offering these prenatal tests, including easyDNA New Zealand – see
www.easydna.co.nz . Ask your
prenatal care specialist or your doctor about these tests – given
that they are relatively recent and not available in all countries,
you will need to get further information and guidance.


Prenatal tests:
Screening tests and diagnostic tests


Screening tests include
urine testing. A urine test is used to determine your blood sugar
levels as well as to check for the presence of protein which could be
a sign of pre-eclampsia, a condition that most pregnant women would
have heard of and that luckily, is rather uncommon. Maternal serum
testing is another test carried out. Don’t be alarmed, although the
term “maternal serum testing” might sound baffling and technical,
all you need to know is that this is a blood test and can help
determine the risk of Down’s syndrome, Edward syndrome and neural
tube defects. This test measures the levels of alpha fetoprotein in
the maternal blood sample. High levels of this protein may indicate
anencephaly or Spina bifida (two examples of neural tube defects).

Ultrasounds are also
categorized as screening tests although they sometimes are also
viewed as diagnostic tests. All screening tests can provide just an
indication of whether the fetus suffers from any of a range of
conditions. Diagnostic tests will be able to confirm whether results
of a screening test were in fact correct.


Amniocentesis,
Chorionic Villus sampling (CVS) and percutaneous umbilical cord blood
sampling (PUBS)


Depending on the week of
pregnancy you are in, one of these three diagnostic tests will be
recommended if earlier tests suggest some genetic or congenital
defect. All three are invasive antenatal tests and all have certain
risks. The one that is most commonly carried out is amniocentesis.
This test involves withdrawing a volume of amniotic fluid from the
amniotic sac. This sample of fluid is then sent to a laboratory for
analysis. Laboratory analysis involves directly testing the fetal DNA
in the sample to determine whether any chromosomal abnormalities are
present. Amniocentesis is also used because it can reveal levels of
alpha fetoprotein (something which cannot be done with chorionic
villus sampling). To reiterate: high levels of alpha fetoprotein
could indicate a neural tube defect such as spina bifida. The one
that is least used of the three is Percutaneous umbilical cord
sampling: this test is carried out at a very advanced stage of
pregnancy (around 23 weeks) and the chances of miscarriage are higher
than with amniocentesis and chorionic villus sampling. Remember, you
do not in any way have to carry out these tests if you do not want
to. However, they can help you get better prepared for the birth of a
special needs child or at least, give you the option of considering
whether to terminate your pregnancy or not.

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