hi everyone if you can believe it it is already week nine of pregnancy and we have been loving
sharing our medical expertise as doctors as well as our in real life experiences with all of you
as we experience pregnancy week by week ourselves yeah so continuing on in our 40-week pregnancy
guide this week we're talking all about prenatal genetic screening and this is a really important
topic because it's the first opportunity to do a test that is going to help you specifically
understand risk for you and your pregnancy this also provides the opportunity to make
some decisions that can help your health and then also the potential health of your baby
based specifically on you and baby's needs yeah so if this is your first time meeting
us i'm sarah and i'm an ob gyn i'm kurt and i'm a pediatrician and we are the doctors bjorkman
welcome back so last week in our week eight video we talked all about the first prenatal
visit and you can check that video out here if you missed it but one of the pieces of that first
visit is talking about first trimester genetic screening specifically looking for chromosomal
abnormalities that your baby might have which are abnormalities with the baby's genetic code
and it can be a complicated confusing process yeah so this week we want to dive a bit deeper into
that prenatal genetic testing both testing for the first trimester and then also testing throughout
pregnancy our goal for this week's conversation is really to pack in a ton of great information
to help you with your conversations with your ob provider both so you can know
what your options are and how those options might affect your pregnancy but before we
get into those details let's talk about what is happening with baby's development in week nine
it's week nine and baby is already the size of a grape or about one inch long and every day they're
getting more and more details that make them all their own they have all their essential organs
now that are continuing to grow their fingers and toes are continuing to get more defined
and they can even bend at their elbows so we want to start with the basics about what a
screening test actually is so a screening test is a very sensitive test that looks to detect disease
in people or babies who do not have symptoms of that disease yet and the goal is early detection
so that you can either prevent or treat that disease effectively or make decisions ahead
of time yeah so the important thing to remember here is that a screening test is not diagnostic
so a positive result on a screening test simply means that you're at a higher risk of having
that disease not that you necessarily have that disease process these are picked up by diagnostic
tests which are a bit more specific and say that a positive result is confirmation of that disease
with prenatal genetic screening tests the goal here is to pick up things early and
so with prenatal genetic screening these tests are looking for changes or abnormalities in your
baby's dna or genetic code and we think of that dna as kind of a blueprint for how your baby's
body should form and develop and so we're looking for changes in that dna with these screening tests
so you may or may not remember from high school biology that every normal human has 46 chromosomes
in 23 pairs so when egg and sperm meet you get 23 chromosomes for mom and 23 from dad
so cool but sometimes when that genetic material is coming together there can be mistakes
there can be big mistakes meaning that you get an extra chromosome or you are missing a chromosome
and that is called aneuploidy the most well-known aneuploidy is called trisomy 21 or down syndrome
so there's an extra chromosome 21 instead of having two you have three there is a wide range
of possible outcomes that depends on the specific chromosomal abnormality that the baby has and that
can be intellectual disability severe intellectual disability structural anomalies failure to thrive
or even a shorter life span chromosomal abnormalities occur in one in every 150
live births and occur even more commonly in early pregnancy as chromosomal abnormalities account for
nearly 50 percent of early pregnancy loss these abnormalities occur with increasing frequency with
advancing maternal age but can occur in mothers of any age notably they are not related to race or
ethnicity the most common aneuploidy is trisomy 21 or down syndrome and occurs in one in every
700 live births other common trisomies include trisomy 18 or edward syndrome which occurs in one
in every 3 000 live births or patau syndrome trisomy 13 which occurs in one in every six
thousand live births there can also be chromosomal abnormalities with the sex chromosome specifically
kleinfelter syndrome which is having an additional x chromosome while still having a y chromosome
occurs in one in every 500 males turner syndrome which is an x chromosome without an additional
sex chromosome occurs in one in every 2 500 live births as a pediatrician i've cared for children
with all of these various aneuploidies and chromosomal abnormalities and it's important to
know that they can have a wide variety of symptoms structural abnormalities and other conditions that
need to be thought of if this is something that comes up on your prenatal genetic screening it's
really important you talk more with your ob provider and also potentially geneticists to
understand what risks they play to your child and what outcomes are likely after birth in addition
to aneuploidy there can also be a smaller loss or gain of the chromosome and that is called a
micro deletion or a duplication now while these are called micro they can actually have huge
clinical effects from a non-viable pregnancy to a life-limiting condition in a newborn
and so risk factors associated with increased risk of chromosomal abnormalities include things
like advancing maternal age a prior chromosomal abnormality in a previous pregnancy abnormality
seen on an early ultrasound in pregnancy or positive prenatal genetic screening and as we
talked about a little bit earlier trisomy 21 18 13 as well as those sex chromosomal abnormalities
your risks all increase with advancing maternal age but those micro deletions and duplications
that we talked about actually don't change very much with maternal age and the risk is about 1
in 270 no matter how old you are so that was a lot of setup to get to the point where we can actually
talk about what your options are for screening and help you be prepared for that conversation
with your ob provider the american college of obstetrics and gynecology or acog recommends that
genetic screening as well as diagnostic options be discussed and offered to all patients regardless
of your age or risk factors then after you talk about it it's up to you to decide if you want
to pursue that testing or decline yeah so it's really really important to sit down and think
about what your specific risk factors are for carrying a fetus with a chromosomal abnormality
and so this is where we encourage you to sit down with your ob provider review your personal history
your family history and then think about what the options are for testing what the outcomes of that
testing is and how it would affect your choices about what to do with your pregnancy we just want
you to be empowered with knowledge to go and have an informed discussion with your ob provider about
what the options are and what is best for you if anything so for us when thinking about prenatal
testing the question was does it help us at all and the two big reasons to get testing would be
one if it was positive would it change your decision about carrying the pregnancy to term
and the other would be does it help plan at all so for us we knew it wouldn't change our decision
at all but it would help us plan as we are big planners um if anything was positive
being people that have cared for pregnancies with chromosomal abnormalities or care for children
with chromosomal abnormalities it could help us plan and find resources in our own community
and so for us that was what pushed us to say you know let's do this testing
and find out to help us plan so when it comes time for screening in your first trimester or a little
bit later if you show up tardy for your first prenatal visit there are two big options when
it comes to screening the first is the classic first trimester screen and this consists of a
blood test and a very specialized ultrasound the other option is a newer test called cell free dna
so the first trimester screen can be done between 10 weeks and 13 weeks and 6 days
the blood test portion of that looks at three specific markers and then combines that with a
very specialized ultrasound where they look at the and measure the fluid filled portion of the baby's
neck called it nuchal translucency and then that gives you a risk of chromosomal abnormalities the
detection rate for down syndrome with the first trimester screen is between 82 and 87 percent now
say you were a little bit late for your first visit and showed up in the second trimester
you could consider what's called a quad screen where they add a fourth additional marker
to this traditional first trimester screening unfortunately this fourth marker doesn't really
increase the sensitivity of this test but it does mean that there is still an option for
this classic screening even if you show up late to prenatal care correct the other option for
genetic screening in the first trimester or at any point in pregnancy after 10 weeks is called cell
free dna yeah so believe it or not throughout pregnancy there are small fragments of babies dna
actually circulating in mom's blood what this means is that this test can
look directly for chromosomal abnormalities in baby by doing a simple blood test on mom
and cell free dna is an excellent screening test it has a 99 sensitivity for detecting trisomy 21
and 13 and a 98 sensitivity for detecting trisomy 18. it also has a really low false positive rate
which means that there's a very small chance that it falsely tells you there is an abnormality when
there isn't one the other fun thing about cell free dna is they can tell you the sex of baby
well before you could see it with an ultrasound so if this isn't something you want to know at
this stage of the game be sure to let your ob provider know other potential screening that
your provider may discuss with you are what we call combined screening and that means it uses
blood tests that is drawn in the first trimester and combines that result with a blood test that is
drawn in the second trimester and these are things like the integrated screen the serum integrated
screen the stepwise sequential screen and the contingent screening all of which your provider
can talk with you about so for us we chose to do cell free dna just because it is the best
screening test that's out there and historically this was a test when it first came out for women
over 35 or women of advanced maternal age so something to make sure you consider
if that is the test you decide you want to do is finding out if your insurance covers it as
more data has come out the indication for this test you know it's such a great test that it
should be offered to everyone um i people who i know who have the same insurance had it covered
by insurance so it was an easy decision for us but you don't want to get hit with a 700
bill and not know that ahead of time so something to think about so as we mentioned earlier all
these tests are technically just screening tests meaning they let you know your risk of having a
baby with a chromosomal abnormality and so with that your question is probably well what happens
next if one of these tests comes back positive so the next step after a positive screening test
would be just a discussion about pursuing a confirmatory diagnostic test like a cvs chorionic
villus sampling or amniocentesis these tests aren't done first right off the bat because they
do require a procedure what that means is both of these tests both cvs and amniocentesis require
an invasive procedure to actually take a sample from within the uterus for a chorionic villus
sampling what that means is actually using a long needle to take a small piece of the placenta this
is standardly done between weeks 10 and 13. for an amniocentesis it uses a similar long needle
to sample the amniotic fluid or the fluid within the uterus itself and this is generally between
weeks 15 and 18. and because of the invasive nature of these confirmatory tests after a
positive screening result your provider is going to sit and talk with you about what your revised
risk of a chromosomal abnormality is now that you had this positive test they're going to talk to
you about what that genetic condition might mean or look like in a baby and they are probably going
to recommend that you see a genetic counselor to get more detailed information at that time
a more comprehensive ob ultrasound is also done to help aid with your decision making about the next
best step so it is week nine of pregnancy and um this week one of my girlfriends told me about this
early gender test that they did to find out if they were having a boy or girl and it's called
sneak peek and i guess you can do this test as early as like seven or seven eight weeks yeah um
and so we thought it would be fun just to see if it worked and do our like soft call yeah gender
surprise it's kind of like some of those other genetic tests we're talking about where it's
kind of looking for those fragments of fetal dna but it's just looking for a y chromosome and if
it finds a y then it's a boy and if it doesn't then you think it's a girl um we're not sponsored
this is something we just get on her it's gotta be fun and it's like an at-home kit they send
you instructions and the whole kit of how to do it you have to like prick your finger and
put a certain amount of blood in a tube it was kind of like a horror show i was not so good at
it um but you're supposed to get the results in less than a week and so it's supposed to be 99
correct based on the reviews i've seen online i don't know if it's that high there were a lot
of people whose weren't correct but we thought it would be really fun yeah we hopefully we'll
have a result later this week and then we'll get to compare it with our own genetic testing later
down the road so we'll keep you posted so that's it for us this week we realized there was a lot to
cover for just a few minutes covering prenatal genetic screening again our big goal this week
was to provide you with information to get you started to be empowered with your conversation
with your ob provider definitely so if you have any more questions or comments please leave them
below and we will get back to you we hope that you are loving this video week by week pregnancy guide
click subscribe and come back and see us next week when we talk all about the 10th week of
pregnancy and what is going on with that see you next week guys we're doctors but not your
doctors anything we've said in this video is for education or entertainment purposes only it is not
medical advice any specific medical questions you have should be directed to your provider