- So this is around 170 milliliters.
That's a full glass!
A fetus is drinking this much in a day
of its own amniotic fluid.
I told you I was gonna geek out in this video.
Hey, y'all! Welcome back.
I'm Mama Doctor Jones, a board certified OB-GYN,
a mom to four, and I'm so excited about today's video.
You see the title,
it's "Fascinating Fetal Facts,"
and the reason I'm so excited about it
is because I genuinely love fetal physiology, embryology,
anatomy, all of these things,
and I love teaching them to you.
I had so much fun looking up information for this video.
I hope that you'll like the video
as much as I enjoyed making it.
If you're new here and you'd like to stick around,
hit that Subscribe button,
turn on notifications so you never miss an upload.
Let's jump in to the video.
(upbeat music)
Fascinating fetal fact number one:
around eight weeks,
they are the size and shape of a gummy bear.
I'm not going to lie.
I wanted to include this one purely
so that I could go buy my favorite gummy bears
and show you.
So, how do we know this?
Utilizing fetal espionage
or what some of you may call ultrasound,
we can actually measure a fetus on the inside
and see how long it is,
but we also get an idea of what they look like.
Around eight to nine weeks,
they are about 20 millimeters in length.
And we measure that
using something called crown-rump length,
which is from the top of the head
to the bottom of the bottom,
from the head to the butt.
And that just happens to correlate almost exactly
with the size of a gummy bear or around two centimeters.
Not to mention, they have tiny little arm buds,
tiny little leg buds,
just the start of formation of limbs
that look just like the limbs on a gummy bear.
I'll throw an ultrasound comparison up on the screen
so that you can see.
If you're one of my patients, I know some of you watch this,
then you've probably heard me say this in clinic before
'cause it's one of my favorite things to tell people
at their eight or nine-week visit.
The baby is the size and shape of a gummy bear
because it just gives you a little bit of an idea
of what's going on in there and how big they are.
Fascinating fetal fact number two
is that they actually breathe in amniotic fluid
to develop their lungs.
That's right.
Something that would kill you,
breathing in water once you are born,
is 100% required in utero to have lung development.
So think about lungs like an upside down tree branch.
This is where my tree branch comes in,
and I pruned it down just a little bit after I got it.
And it's a little sparse on this side,
but I think it still makes it
for a decent explanation. (chuckles)
From about week seven to 24 of pregnancy,
the lungs are really developing their structural shape.
Meaning, they're kind of growing into that tree branch.
So if you imagine at first it's just a tube,
it branches into two,
those get more branches,
and then the leaves on the outside are the alveoli.
That's kind of what's going on from seven to 24 weeks.
And this process highly relies
on mechanical stimulation inside the lungs.
Meaning, the baby is expected to breathe in fluid,
help to expand that mechanically,
and push it to keep growing to create lungs
and all of the oxygenation space
that they will eventually need.
So fluid goes in, stretches everything out, fluid comes out.
Over and over and over from week seven to 24.
And eventually, that creates lungs.
And let me remind you that you're expecting your lungs
to work immediately upon birth.
Even though for the last 38 weeks,
they've been completely submerged in water.
Because remember, on the inside,
your lungs don't have anything to do with gas exchange.
All of that is going on at the level of the placenta
when you're a fetus.
Despite that, you still come out
and expect them to work right away.
So you can imagine, as I'm describing this to you,
that if there was not amniotic fluid around the fetus
during these key times,
that their lungs won't even develop.
And that's exactly what happens in a situation
with anhydramnios or a lack of amniotic fluid.
This is called pulmonary hypoplasia,
and it's just failure of lung development related oftentimes
to a lack of fluid around the fetus.
And this can happen for a variety of reasons.
Some of the more common reasons
are somebody's water breaking way too early;
or renal agenesis,
meaning, the fetus never developed any kidneys.
So I just told you,
if the fetus never developed its kidneys,
then there may not be any amniotic fluid around them.
Why?
What do kidneys have to do with creation of amniotic fluid?
Well, that brings us to our next fascinating fetal fact,
which is that amniotic fluid is basically fetus pee.
Let me back up.
So, actually starting in the early second trimester
or late first trimester,
most of the amniotic fluid is fetal pee.
Prior to that, there is fluid,
and we're not actually 100% sure where it even comes from.
Even in an anembryonic gestation which is a pregnancy
that never actually develops a fetus or embryo,
you may have heard it called a blighted ovum,
the gestational sac still has fluid in it.
So we know early on that this fluid is not coming
from the fetus itself.
However, after about week nine to 10,
the kidneys start their rudimentary functioning
and the fetus starts drinking the fluid that it had
and peeing out more.
I'm gonna throw in an ultrasound video here of my baby, Pax,
when he was a tiny fetus learning how to swallow.
And I was really, really lucky to catch this on ultrasound.
And I am so thankful I have it
'cause it's such a great video.
And you can see that he's opening his mouth,
taking in fluid, swallowing.
Eventually, that will go down to his kidneys
and he will put it into his bladder and then pee it out.
And that's the continual process of creating amniotic fluid
after about the ninth to 10th week
when the kidneys finally start functioning a little bit.
So by 30 weeks,
a fetus is actually drinking
about 170 milliliters of fluid a day
and peeing out up to 40 milliliters of fluid per hour.
That may not sound like a lot to you,
but let me show you how much it is
and then explain to you how much we actually pee out.
So I'm gonna show you using this syringe.
It holds about two milliliters of fluid.
How much exactly 40 milliliters of urine per hour
that a fetus is peeing out
by the third trimester actually is?
One, two, three, four, five, six, seven.
I should have bought a bigger syringe.
Eight, nine, 10, 11, 12, 13, 14, 15, 16, 17.
It's gonna overflow!
18, 19, 20.
That is 40 milliliters of fluid.
This is a full little, I guess, shot glass
of a fetal pee. (chuckles)
I think that's crazy!
Now, let me make this make sense to you.
If you were in the hospital
and we were monitoring your urine output as an adult,
this would be an acceptable amount of urine per hour
to know that your kidneys were functioning fine.
I know, it's so wild to me
that a fetus at 30 plus weeks
is peeing about that much in an hour.
Now, let's look at
how much amniotic fluid they are swallowing
over the course of a day.
I'm going to show you how much they drink in a day
which is around 170 milliliters.
80, 120.
So this is around 170 milliliters.
That's a full glass!
A fetus is drinking this much in a day
of its own amniotic fluid.
I told you I was gonna geek out in this video
because I love this so much,
but that is so incredibly fascinating to me.
It's so incredibly fascinating to me
that they drink their fluid,
they create more by peeing it out,
and they replenish their own amniotic fluid.
And in the process, they're learning how to swallow,
they're learning how to breathe.
With that lung development
that I told you about in the last one,
it's wild.
I love it so much.
This process of swallowing and creating pee
can be very sensitive too.
So if anything goes wrong
at any of the levels of creation of urine,
this can lead to major issues in the fetus as well.
So if there's placental insufficiency,
if there's heart problems,
if there's problems with swallowing,
problems with the kidneys, problems with urine output,
posterior urethral valves which keep the urine
from actually coming out after it gets into the bladder;
all of these things can cause major issues
that have downstream effects.
There has to be fluid to develop the lungs.
There has to be kidneys to develop the fluid.
All of these things are really important.
So all of these processes are really sensitive.
And to me, that says,
it is absolutely miraculous
that any of us learned to function as a fetus,
and then at birth learned to function
as not a fetus anymore.
It's wild.
So they're in there drinking their own fluid, peeing it out,
drinking again, breathing it in to develop their lungs,
but what else are they doing?
For the next fascinating fetal fact,
we're going to talk about fetal sleep.
That's right, they sleep.
In fact, about 20 minutes out of every hour,
they will be awake
and most of the other time they are sleeping.
Sometimes, even up for 50 minutes at a time,
they will take naps.
The closer you get to term, the more a fetus sleeps.
And actually by the time you are full term,
they're spending like 95% of their day asleep.
Now, importantly, that does not mean that no movement
or decreased movement is normal as you get to term.
They still move during periods of sleep.
And if you feel like your baby is not moving or moving less,
you need to let your doctor or midwife know.
Around 26 to 28 weeks,
you can actually start to see on ultrasound their eyes doing
that classic movement that we associate with REM sleep.
It's really interesting to watch on ultrasound,
but even more interesting than that is you can wake them up.
I know, I know.
You're never supposed to wake a sleeping baby,
but sometimes when we do something called a nonstress test
where we're monitoring the fetal heart rate,
we need to make sure that the heart rate looks like it does.
We're looking for these various patterns.
Because the fetus is asleep and not because it is in danger.
When we're looking at a fetal heart strip,
we're looking for a baseline that's within the normal range,
which should be somewhere between about 120 and 160.
We're looking for it to move around like this
that's called variability.
You don't want it to be a flat line.
And we're also looking for something called accelerations.
Sometimes, when you're monitoring,
they may not have accelerations because they are sleeping
or it may be because they are in danger of some kind.
And so we can delineate that either
by just continuing to monitor for an extended period of time
for a couple of hours,
or by doing something called vibroacoustic stimulation
to wake them up out of that sleep state.
And this is basically just a little vibrating tool
that you put on the belly.
And usually, after you do that,
they wake up, they start kicking around more
and you start seeing those accelerations
and their heart rate.
And you can say, "Yep, everything looks great.
"It's okay for you to go home."
The next fascinating fetal fact
is actually about their head.
Fetuses actually have skull bones which are not connected.
If you feel your head,
it shouldn't move around.
Your skull is one piece.
But a fetus, not one piece.
In fact, a newborn when they're born has about 94 more bones
than you have when you reach adulthood.
Over time, they fuse together to form that 206 bones
that make up a normal human adult skeleton.
As far as the fetal skull is concerned,
you have two frontal bones,
two parietal bones, and an occipital bone.
And they are connected with something called sutures.
And in those suture lines is some fibrinous material
that allows a little bit of flexibility in the skull,
and the reason for this is two-fold.
So you need to be able to move the skull
around a little bit as you're coming through the birth canal
so that it doesn't injure you,
and you have to be able to allow for growth of the brain.
In those first years of life,
a baby is growing its brain at a rapid pace.
And if the skull couldn't expand,
then that wouldn't be able to happen.
So those sutures and the fibrinous material in them
allow for expansion of the skull
until the brain reaches its normal size.
Over time, that fibrinous material in the sutures
is replaced by hard bone.
And you eventually get to the point
where your skull is what I hope y'alls is like now
and doesn't move around.
You also have two fontanelles,
an anterior and poster fontanelle.
Y'all might know these as a soft spot.
The anterior one here closes by the time you're about two,
and the posterior one back here closes about three months
after you were born.
It was to serve the same purpose,
to allow for growth and expansion of the skull
as the brain gets bigger.
And you can actually see on an adult human skull,
the suture lines from where
that fibrinous material was replaced
and created their normal full skull that is one bone.
Which interestingly, we also use to tell what position
that a fetal head is in during the birth process
because you can identify where each of the sutures are
and decide which way the fetus is facing.
So, you might've heard me say something called OP
or occiput posterior.
What that is referencing is this occipital bone
in the fetal skull and where it is facing
in relation to the person giving birth.
So, if the occiput is posterior,
that means baby's coming up face up,
sunny side up, star-gazer.
Not the way we really liked them to come out,
but still okay.
And if we say occiput anterior,
it's facing the floor
which is a little bit easier way to give birth.
If that fusion of the skull bones happens too early,
so those sutures
and their pliable material holding them together
are replaced by hard bone too soon,
you get a condition called craniosynostosis.
And this causes the brain and skull
to grow in a misshapen way
and doesn't allow for optimal growth.
If it happens in utero,
it can be really dangerous as well.
For our next fascinating fetal fact,
we are getting into the nitty-gritty of circulation
because their circulation is completely different
on the inside than it is on the outside.
And the first breath they take drastically alters the way
that their blood flows through their body.
That's right.
They have completely different circulatory system
than you and I.
And that's where my handy-dandy whiteboard comes in.
I'm gonna draw it out for you.
(upbeat invigorating music)
And basically, what you're looking at here
is the placenta is serving as the gas exchange in a fetus.
So, instead of having oxygenated blood going
into the body from the heart,
you have oxygenated blood leaving the placenta
through umbilical vein, so through the umbilical cord.
It basically bypasses the liver, some goes to the liver,
but because all of the exchange to remove toxins and stuff
is done at the level of the placenta,
they don't have to send all of the blood
through their liver to get cleaned out.
And it goes through the ductus venosus,
which is not something that we have
once we are on the outside.
And I'll explain to you what happens to it.
And then through the inferior vena cava,
which remember in somebody who is functioning
on the outside, this is not oxygenated blood;
but on the fetal side,
it is oxygenated blood to the right side of the heart.
Now, we already have oxygenated blood,
so we don't have to go to the lungs.
We bypass the lungs through a hole in the heart
called the foramen ovale.
So oxygenated blood bypasses the lungs.
A little bit goes there just for the tissues to be healthy,
but it doesn't go there to get oxygenated.
It had got his oxygen here at the placenta.
And then, out into the aorta and to the body.
So, it totally bypasses
or mostly bypasses the liver and lungs
because they don't have to function like they do
when you're on the outside.
Goes to the body,
now you have deoxygenated blood.
It's going through the umbilical cord,
in the umbilical arteries, and back to the placenta
to reoxygenate, reclean, and come back and do it all again.
So how does it go from that to what we have on the outside?
'Cause it has to happen fast.
When you are on the inside,
the vascular resistance inside the lungs is really high.
Blood, like all liquids, takes the path of least resistance.
The path of least resistance
is going to be going through that foramen ovale
and that ductus arteriosus,
instead of through the pulmonary vasculature.
However, when you come out
and you take that first deep breath,
there's a massive drop in the vascular resistance
inside of the lungs.
And what that does is create a pressure system
that closes the foramen ovale in the heart.
So that hole in the heart goes away.
Now, things can go wrong.
Sometimes, people have to have this surgically fixed.
But in a perfectly functioning system,
which most of us have,
that immediately closes, the ductus arteriosus closes.
Part of that has to do with a drop in prostoglandins,
which is a hormonal response,
but those two close.
And then how does the ductus venosus
which bypasses the liver close?
Well, if you will remember,
the umbilical vein is what was feeding that.
What happens after you're born?
The cord is clamped and cut and stops flowing.
This also creates a sudden pressure change
and closes the ductus venosus.
The fact that you have a completely different way
that your circulatory system functions
that changes immediately when you breathe in at birth
is incredible to me.
Mind blowing.
I know, I told y'all I was gonna geek out this whole video
and I'm doing it.
I just really hope that one of you likes this video
as much (chuckles) as I do.
Moving on to our final fascinating fetal fact
for this video.
And that is, sometimes they have teeth.
Not just the teeth that exist under your gums
that you have when you are born but actual teeth.
This is called a natal tooth.
And occasionally, a baby will be born with a tooth
that has erupted during the fetal stage.
It usually is not problematic.
It's usually just a random thing.
I've seen it a couple of times.
It can occasionally be associated with really rare syndromes
that I'm not even going to attempt to pronounce.
But most of the time, it's not harmful.
As long as it's not loose or causing problems with nursing
or causing cuts on the tongue or anything like that,
it's usually just left there,
and baby got their first tooth a little bit early.
All right, y'all! That's it for today.
I hope that you geeked out
and loved this fascinating fetal fact video as much as I do.
If you're not subscribed and you wanna be,
hit that Subscribe button and turn on notifications
so you never miss an upload.
And I will see you next Monday.
(upbeat music)
This is not my house,
and I don't have hardly anything here
that I can use for my demonstrations.
So, I'm gonna run to the store.
Y'all can come with me if you want.
Hi! Yeah, so I changed clothes, obviously,
because I'm not above putting on a scrub top
to film a video,
but I am absolutely not going to the dollar store
in my scrubs.
I'm gonna run in and get some supplies
so that we can get this video done.
I have never been so excited about a video.
Maybe the vaginal discharge video,
but I love this topic!
Let's go.
(upbeat music)
I got our supplies.
I need to stop one more place and get one more thing,
and then go home and film this video.
Also, there's a dog out here.
And I am definitely a dog person,
but a week or two ago,
I got attacked by a gang of schnauzers.
And one of them jumped from the ground all the way up
and bit me on the arm.
The bruising is almost gone,
but I had to go get antibiotics
'cause I have a puncture wound from its tooth there.
So, I have weird anxiety about dogs now.
And there's just this dog out here staring at me.
It's threatening me.
So, I'm gonna go,
and I'll see you in a minute for one more stop
and then home for this video.
(upbeat music continues)
Let's go home. (chuckles)
All right, we have all of our things.
Now, we can actually jump into the video.