Pregnancy, childbirth, and everything
associated with it is in my personal
opinion the most incredible process
in all of human biology but it's not all
lollipops and rainbows and as beautiful as the
children may be, the process of creating them,
let's just say it can come with some
uncomfortable consequences and in today's
video with the help of the cadavers here
in the lab, we're going to discuss some of
the changes that occur to the mother's body
during pregnancy, such as morning sickness,
fatigue, changes in taste and we'll even talk
about what happens to the internal organs as
that growing uterus creates that wonderful
fetus. Gonna be a special one. Let's do this.
[Intro]
Now, obviously, I don't have a uterus and
I've never grown and carried a baby but I've
been fortunate enough to witness the process
twice in my lifetime now and I can say with
the utmost confidence, it absolutely blows
my mind. There aren't enough adjectives in
the English language to describe
just how truly incredible the process is.
So, I want you to know that my goal with
this video isn't to focus on the negative
aspects of pregnancy. Instead, I
just want to highlight some of the
most commonly experienced symptoms that
come with pregnancy. In a future video,
we can discuss all the many beautiful
things that also come along with pregnancy.
First up is morning sickness but I want
to be clear right from the start. Morning
sickness is a misnomer. It can happen at any
time of the day and has no obligation to go
away simply because you ate lunch but we still
don't know the exact cause of morning sickness
but it seems likely that the hormone HCG is at
least partially if not entirely responsible.
HCG stands for Human Choronic Gonadotropin and
it's secreted by the precursor to the embryo
called a Blastocyst which is just a few steps
away from the egg fertilization and then over
time it'll eventually start being secreted by
the placenta itself and essentially tells the
body and the uterus "hey, we're pregnant,
let's just keep things going how they are."
You see, HCG levels double every 48 to 72 hours
during the first 12 weeks of pregnancy. That
is amazing to me. That means this hormone is
doubling every two to three days for 12 weeks,
but then it'll peak. And then it'll actually
decrease for the remainder of the pregnancy.
If you have higher than normal levels of HCG,
that could mean there is a multiple pregnancy
such as twins or triplets or it could also
mean there's an issue with the pregnancy such
as down syndrome. But for most individuals,
morning sickness tends to disappear around
weeks 12 to 16 which coincides with that
decrease in HCG so it seems reasonable to assume
that it at least plays some role in the symptoms.
It's also possible that the hormones progesterone
and estradiol play a role in the symptoms
considering they have an effect on a wide variety
of structures and tissues in the body including
the stomach and intestines, which makes a ton
of sense when it comes to nausea but again,
we still don't have a clear understanding of the
mechanism. we can't say oh, it's because of this
much estrogen and progesterone and HTG that's
why you get the symptoms. more than likely,
they all play a role in some way
but I want you to take a step back and
try viewing morning sickness through an
evolutionary lens because if you do that,
there's possibly a real good reason why it
exists and that is to protect the growing
embryo and fetus during this most vulnerable
stage of development, the first trimester.
If you're nauseous, then, you're probably
going to be more selective with the foods
that you eat. Meaning, you're potentially limiting
harmful substances from getting into the body and
negatively impacting the pregnancy. This is just
a hypothesis but for me personally, it makes a
ton of sense but depressingly some individuals
get a more extreme form of morning sickness
that in some cases can last the entirety of the
pregnancy, which is just as awful as it sounds.
The condition is called Hyperemesis Gravidarum
and it's actually pretty difficult to diagnose
and parse out is this just normal morning sickness
or do we have a real problem on our hands but it's
commonly described as being excessive vomiting
that can lead to weight loss and exhaustion and
fatigue and result in higher than normal
levels of ketones in the urine and blood.
If you picture debilitating nausea that can have
a dramatic and negative effect on the pregnancy,
you pretty much got it but again, for most individuals,
most of the time, morning sickness
does go away in the second trimester.
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Next up is fatigue and while there isn't a
single cause for fatigue during pregnancy,
a big factor is the hormone progesterone or
more accurately, a metabolite of progesterone
called Allopregnanolone which increases the
affinity of a neurotransmitter called GABA.
Now, this is a bit in the weeds but just
stick with me here. GABA has a wide variety
of functions but it's the main inhibitory
neurotransmitter in the brain and spinal
cord and activation of GABA receptors leads to
drowsiness or just an overall more relaxed state.
As progesterone levels increase during
pregnancy, the hormone is metabolised,
meaning allopregnanolone levels will also increase
and allopregnanolone will bind to those GABA
receptors increasing their responsiveness to
GABA making you feel more relaxed than tired.
So basically, higher progesterone levels
means higher responsiveness to GABA which
leads to drowsiness. Now, fatigue typically
ends for most as the second trimester begins
only to come back again in the third trimester
but that's a whole other can of worms but
this is interesting because progesterone levels
actually increase over the entirety of pregnancy.
You see, one of progesterone's primary functions is to create
a healthy uterine environment for
the embryo and growing fetus. So,
it makes sense to have high levels of it
throughout the entire pregnancy. This goes
to show that while progesterone plays a big role
in fatigue, it doesn't play an exclusive role.
Plenty of other hormones and their levels are
going to be changing throughout the pregnancy
and when you factor in the stress to the
body and mind from the whole situation,
I mean, we have morning sickness,
an increase in blood volume. I mean,
just thinking about the fact that there's a
baby growing inside of you, I mean, when you
factor all that together, I mean, it's not all
that surprising that you feel kind of tired.
Another extremely common experience during
pregnancy is a change in taste. Typically
described as a metallic or bitter taste in the
mouth. A 2004 study published in the journal,
Chemical Senses found that 93% of women reported
a change in taste during their pregnancy.
Now, Self-reported studies are not the
most reliable studies out there but 93% is
extraordinarily high. While the mechanism
isn't well understood, it's likely that
estradiol which is a type of estrogen plays
the biggest role in these strange tastes.
A 2021 study published in the American
Journal of Physiology, Endocrinology,
and Metabolism found estrogen receptors in
taste cells. Specifically those involved with
tasting fat. This means there's likely
a difference in tasting ability between
males and females considering females
have more estradiol in their system.
I mean, take pregnancy out of the equation,
males and females likely taste food differently.
in regards to pregnancy, estradiol and
estrogens are going to fluctuate beyond
normal ranges obviously for quite some time.
Most likely this is what's responsible for
those altered taste but I want you to think
about this - eating certain foods literally
becomes more intense which could explain
certain foods just must be avoided, right?
You talk to pregnant women, some foods just under
no circumstances will they even entertain the
thought of eating that food while other foods,
even strange ones can become more enticing.
And lastly, the third trimester just
looks uncomfortable and for good reason
too. There's only so much space in the human
body and now you have this gigantic uterus
that's just pushing everything out of
the way. Let me show you what I mean.
You are looking at an anterior view of both
the thoracic and abdominal pelvic cavities. So,
there's a lot of tissues and structures and
organs to look at here so let's just kind of
real quickly. This yellow apron that's draping
in front of the small intestine, this is called
the greater omentum and it's a fatty tissue but
it's also made of something called peritoneum. So,
you can see the intestines are going to be right
behind it but real quick, let's also look up here.
You can see the diaphragm muscle
which is a skeletal muscle that is draped on
top of the liver here and then to the left,
we have this pink organ which is the stomach and
you're only able to see a portion of it but we're
getting to like the pylorus and then it's going
to be transitioning into the small intestine
and then - oh, also, underneath
the liver is going to be the gallbladder.
We can also see the two lungs and then the
heart still in the pericardial sac but if I
go ahead and reflect that greater omentum
back, you can see part of the transverse
colon which is kind of interesting. This
might even be a redundant colon because
that normally doesn't take this unique pathway
and then right here we have the small intestine
which I can then reflect back and that
allows us to see into the pelvic cavity,
into the uterus. So, let's go ahead and
zoom in so we can talk about the uterus.
So now that we've zoomed into the pelvic area,
let's go ahead and orient you so you know what
you're looking at. This right here is
the sigmoid colon and then that would
transition into the rectum which is going to be
behind this structure here which is the uterus.
Now, the uterus can be divided into different
sections. This top portion here is called the
Fundus, which will come back to in a moment.
Then, we have the body of the uterus and then,
what you can't see because for one, it's
embedded inside the connective tissue and two,
the camera angle just doesn't really work all that
well, is what's known as the cervix of the uterus.
Now, cervix actually translates to
neck. Think like cervical region of
your vertebral column. So, the cervix of
the uterus is the neck of the uterus. Now,
again, we'll come back to the fundus in
a moment but to the side of the uterus,
we then have what's called the uterine tube or
also known as the fallopian tube and I'm going
to go ahead and lift that out of the way and
we're going to try to make this thing visible
here. This is an ovary and there would be
another one obviously on that other side as well.
Now, fundus actually translates to end. So, this
is the end of the uterus and the reason why it's
important is because your OBGYN or your midwife
can actually use the position of the fundus to
help determine how far along in the pregnancy you
are. So, they'll do that by measuring the distance
the fundus is away from the pubic bone which you
might be able to see a bit to the bottom of your
screen but how far along this is has a one-on-one
correlation to how far along you are in pregnancy.
So, what I mean by that is, let's say, the fundus
is 20 centimeters away from that pubic bone,
you are 20 weeks along and this starts to show
up around 20 weeks but twenty-four centimeters,
you're twenty-four weeks. 32 centimeters or 32 weeks,
so on and so forth. Now, here's the crazy part. The fundus,
it's going to go all the way up to the xiphoid
process which is at the base of your sternum.
If you do this at home, just be very careful
because it's going to hurt a but there is a
sharp point at the base of your sternum. That
is the Xiphoid process and the fundus is going
to come all the way up there when you
are full term. That is crazy to me. I mean,
just thinking about all the structures
that are going to shift, absolutely nuts!
So, now, let's take a look at all the structures
that are going to be shifting as the uterus
is growing. So, again, we have the greater
omentum here and the small intestines. So,
what happens, as uterus starts growing, the
small intestine are going to start moving and
shifting interiorly and superiorly. So,
they're going to be kind of like resting
on top of the uterus like a shelf. So, you can
picture all of it just flaring out and resting
on top of it. The same goes for the greater
omentum because it would be on top as well.
And as it's pushing upwardly, it's also
going to have an effect on the stomach. So,
what's going to happen is it's going to lift the
stomach and it's kind of hard to tell from what
we're looking at. The stomach is going to start
also transitioning into the horizontal plain. So,
the pylorus of the stomach is going
to start pointing anteriorly and it's going
to become flat and this is a big cause of
acid reflux or your gerd type symptoms.
A lot of times you'll hear pregnant women say
like I'm hungry then they eat a little bit and
then they feel full but they're not really full
because the stomach is so compressed. It just
kind of feels fulls but that also can squeeze
out gastric juices into the esophagus and can
contribute to acid reflux type symptoms. Again,
definitely not the most comfortable of situations.
The liver is also going to get pushed as is the
gallbladder and so, as the stomach and liver are
pushing into the diaphragm, they're going to start
pushing into the lungs and the heart. The heart
will actually shift in pregnancy and so again,
this is hard for me to do because the cadaver
is preserved and everything is kind of like
situated in the body but the heart would also,
like the stomach, start to project anteriorly
and come closer to sternum because the sternum
would be just right in front of it so the heart
is going to come towards that sternum and lift.
The lungs are also going to start shifting
and getting compressed and you might think
that this could relate to like some kind
of labored breathing but interestingly,
during the shift, the ribs, which again, we've removed here,
the ribs are also going to start flaring
out and actually creates more space.
So, as the ribs come out, it creates space that the lungs,
so even though the lungs are getting
compressed, they still have more space
to flow into so you don't really see
difficulty in breathing. But I mean,
that is so much shifting that is all going to
happen because again that fundus has to come
all the way up towards the xiphoid process which
would be - because here's the sternum, the xiphoid
process is going to be right here above the liver
so everything is going to be pulled up in the
superior direction and flaring anteriorly. It is
absolutely incredible and definite uncomfortable.
Now, there are plenty of other changes that
occur in a mother's body during pregnancy
such as changes to liver metabolism, kidney
function, peristalsis in the digestive system,
and more. So, be sure to let us know in
the comments below what other aspects of
pregnancy you'd like us to cover
in future videos but thanks again for
watching everybody. I hope you enjoyed
it and I'll see you in the next video.