Genetics   Prenatal Video
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Genetics Prenatal Video


Hello my name is Samone Schneider and I am
a certified genetic counselor I work at Jacobi Medical Center in New York City specifically
I work in the women’s health services I generally see patients for referrals for prenatal
preconception and oncology so first today I wanted to start off by giving a little bit
of background information in you know what is a genetic counselor and what do I do generally
because I know we are an uncommmon field so when I meet with a patient I evaluate their
personal and family history and I determine if any genetic testing is appropriate if genetic
testing is appropriate I determine what are the different options and the different ways
we can go about that testing I then present the different options to the patient and I
discuss the risk benefits and limitation of each test and I also discuss how those tasks
could impact the patient the pregnancy or the family and I then make you know recommendations
based on the results of those tests so in a nutshell that’s generally what I do however
there’s a lot more to it so if you’re interested in getting more information please feel free
to reach out to me so to go back to our topic today I would like to discuss genetics in
a prenatal setting specifically I’m going to be discussing different screening options
as well as different diagnostic options so with the help of your professor today my hope
is that you can also see my PowerPoint so I’m going to flip to my second slide now
so this is a picture of our chromosomes so as you know when we are talking about our
genetics we are really talking about our DNA our DNA is packaged in these chromosomes as
I think you have reviewed with you professor humans have 23 sets of chromosomes in each
set we get one from our mom and one from our dad so the first 22 sets are what call automsomal
so these are you know chromosomes we get regardless of our sex so whether you are a boy or a girl
you can inherit these just the same way our last set so our 23rd set those are our sex
chromosomes so women typically have two Xs and Men typically have an X and a Y so that
Y is actually what determines whether or not an individual is a male or female so you may
have noticed I said typically there are quite a few conditions that occur because of the
loss or a gain of one of those sex chromosomes and really they’re actually quite a few considtions
so I’m not going to go into as much today but just something to be aware of so if we
flip to our next slide this is a picture of an individual that has downsyndromes so I
picture of their chromosomes so you may notice that they have an extra copy of the 21st chromosome
so the reason I am starting here is because there are a number of conditions that are
causes b by either the gain or the loss of a chromosome these conditions are actually
quite common and that’s why we actually offer screen to every women for every pregnancy
so this is really where we’re going to start today as our jumping off point so Down Syndrome
is the most common example of this and you may notice that the other name for Down syndrome
is trisomy 21 so trisomy is really just saying you know it is a third copy of the third chromosome
so its just a fancy way of saying that so for example if I say trisomy 1 I’m saying
that there are 3 copies of chromosome 1 trisomy 7 3 copies of chromosome 7 similarly monosomy
is referring to a single copy of that chromosome instead of 2 so with Down Syndrome as I mentioned
is the most common example of this down syndrome is also the most common cause of intellectual
disability so if you flip to the next slide you’ll see a picture of three individuals
with Down Syndrome so the first thing I typically describe to patients is that with individuals
with Down Syndrome you know they typically look more like one another than other members
of the family so we you know refer to this as dysmorphic features so these are slight
abnormalities that cause the children to look more like one another so exactly for a genetic
test I would go through exactly what those differences are but for now for now you can
probably just you know see that these indiviuals look a little different so you know as I mentioned
it is the most common cause of intellectual disability it is important to know that Down
Sydrome is actually classified as a mild to moderate intellectual disability many people
think of down syndrome as one of the worst genetic conditions you being very severe and
while certainly it will impact an individual’s life it is important to remember that intellectual
disability is actually more on the mild to moderate end of the spectrum so speaking of
spectrum you know Down Syndrome itself really exists the one a specturum so what thing we
know that is true for all individual that have been diagnosed wtih Down Syndrome is
that again they look a little different than other individuals in their family and they
have some level of intellectual disability but there is many other things that can go
on with an individual that is diagnosed with Down Syndrome so you know on one end of the
spectrum we have the individuals that you may have seen in the community or on TV these
are individuals who typically have jobs they have families and they sometimes live alone
certainly those individuals exist they do quite well on the other end of the the spectrum
there are children with Down Syndrome who you know are very severely affected so when
thinking about Down Syndrome there are some defects that are more common so for example
heart defects are more common so these are congenital heart defects meaning some one
was born with something wrong with their heart similarly they are more likely to have problems
with their digestive system more likely to have problems with their eyes as well as problems
with their hearing so for some individuals there can be very severe complications at
birth not all of these childen leave the NICU and some individuals with intellectual disabilities
that are more severe it may never be possible for them to live on their own so you know
that’s always something I have to stress with individuals you when a child is diagnosed
with Down Syndrome you we don’t know which side of the spectrum their child is going
to be because unfortauntely all we can see is that extra chromosome so you know really
I’m focusing on Down syndrome because again it is the most common but it is not the only
trisomy we look for during pregnancy so in my next slide you’ll see two other examples
and this is trisomy 18 also known as Edward’s syndrome and trisomy 13 also known as patau
syndrome so with these two conditions you may have noticed you know that you haven’t
heard of them as much or haven’t really seen indiviuals with this condition like Down
Syndrome and that is because they are much more severe than Down Syndrom so with both
of these conditions it’s very common for individuals to miscarry during you know the third trimester
or late during the second trimester really throughout in addition it’s very common for
these children to pass away shortly after death birth so many of these children won’t
actually mka eit to a year of life so with these two conditions really that intellectual
disability is actually defined as much more severe than Down Syndrome so in addition to
being more severe than Down Syndrome they are also more rare however they are two more
trisomys that can result in what we call call live birth so we do screen for them as well
so you may notice I used the words live birth so for example we can have an extra chromosome
or missing chromosome really anywhere but if someone has an extra chromosome one where
its trisomy 1 this really isn’t going to be something that’s compatible with the likely
this is likely not a child that’s going to make it past the first trimester and very
similar to many of the others so the other exception is our sex chromosome you know many
different things can happen with those too many too few they are a little bit more forgiving
when it comes to that so because of this as I mentioned we like to offer screening to
every woman during pregnancy the reason for that is that with these conditions where you
have an extra or missing chromosome the vast majority of the time they just took occur
by chance so many individuals who have Down Syndrome they are the first person in their
family to be diagnosed with Down Syndrome and you know it’s not anything that mother
ate or did during her pregnancy it really did just occur by chance so with Down Syndrome
95% of the time it follows that inheritance and it really did just occur by chance really
only 5% of the time can there be a more hereditary component to Down Syndrome

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