[Music]
our genetics are determined by the
chromosomes in our cells you have the
option to screen for a number of genetic
disorders in pregnancy
some examples are Down Syndrome Turner
syndrome and chromosomal trisomies
genetic disorders occur if the fetus
does not have the usual number of
chromosomes or if there has been a
mutation to an important part of a
chromosome mutations can be inherited or
they can happen spontaneously during
conception there are two kinds of
testing screening and diagnostic a
screening test is a blood test that
indicates the probability that the
pregnancy has a chromosome abnormality
it is non-invasive meaning there's no
possibility of harm to the pregnancy to
have this blood test drawn for women who
are low risk a blood test is drawn from
the mother in the first and second
trimester a woman is typically
considered low-risk if she will be under
age 35 at delivery hasn't had a prior
pregnancy with a chromosome abnormality
and has no family history of genetic
abnormalities six types of blood markers
are evaluated and this information is
combined with an early ultrasound
evaluation of the fetus to give a risk
estimate for how likely it is that the
fetus will have an extra chromosome
women age 35 and above or who have a
personal or family history of having a
baby with a chromosome abnormality or
who have screened positive with the
low-risk blood tests are considered
high-risk for a genetic disorder
high-risk women have the option for
cell-free DNA testing this is also a
non-invasive blood test to evaluate the
risk of chromosome abnormalities but it
has a lower risk of false positive
results it's a more expensive test and
it's typically covered by insurance for
women who meet the high risk criteria
importantly both kinds of screening
tests can be falsely positive or more
rarely falsely negative if a screening
test is positive the option will then be
given to follow up with a diagnostic
test for a definitive diagnosis
a diagnostic test uses a tiny sample of
your placenta or the fluid around the
fetus to directly measure the
chromosomes that the fetus has there are
two ways to do this either through
chorionic villus sampling or CBS or
amniocentesis both tests are done by a
maternal fetal medicine specialist in
their office no anesthesia is required
chorionic villus sampling is when a
needle is used to take a tiny sample of
the placenta either through the abdomen
or through the cervix the placenta has
cells with chromosomes that usually
match the fetus it can be done between
ten and thirteen weeks of gestation in
an amniocentesis a needle is used to
sample some of the amniotic fluid around
the fetus the amniotic fluid carries
cells that have chromosomes matching the
fetus it can be done after 15 weeks of
gestation both methods carry a very
small risk of pregnancy loss typically
around one and 450 to one and 900
depending on the gestational age of the
fetus and the experience of the provider
doing the procedure because both methods
sample the actual chromosomes very
detailed testing is available and the
results are highly accurate genetic
screening is optional it's your choice
whether to undergo prenatal testing even
if you have a positive screen you don't
have to undergo diagnostic testing on
the other hand there are some parents
who desire to skip the screening and
move straight to diagnostic testing it
can be helpful to think how you would
use the results of the prenatal
screening tests for some parents the
information may lead them to end the
pregnancy for others having the
information would help them to prepare
for having a baby with a genetic
disorder and plan for the medical care
their child may need other parents may
not want to know this information at all
before the child is born we are
fortunate to live at a time when this
kind of testing is available and you as
a patient have choices at each step it's
important to discuss with your provider
any questions or concerns you have so
that you feel empowered to choose what
is right for you and your family
you