- [Voiceover] One of the most amazing moments
for a woman is when she finds out she's pregnant,
or I guess I should say when her
brain finds out because her body
is already aware of it from several weeks before.
So much so that by the time a woman finds out
that she's about to be a mom,
her body has already undergone several changes
to prepare for that growing baby.
One of the first and most important changes
that the body makes is that it
realizes that it needs more oxygen,
which means that it needs more red blood cells
to carry the oxygen within the blood.
And in order to do that,
the level of a hormone called Erythropoietin
have to increase.
And Erythropoietin is this hormone
that stimulates the bone marrow
to increase production of red blood cells.
And those levels don't increase by just a little.
They increase up to 50%.
In fact, if the pregnant body could have its
way with things, the amount of red blood cells
would increase by something like 20% to 30%
over the course of a pregnancy.
But what actually ends up happening
a lot of the time in pregnancy,
is that women become anemic,
so the hemoglobin and the hematocrit values,
which are measures of the amount of red blood cells
you have in the blood, decrease.
Instead of increasing, they decrease.
And that can happen for
a couple of different reasons.
The first reason is something that
happens in normal, pregnant women,
and that is that the plasma volume,
which plasma is like the liquid component of blood,
the plasma volume increases more
than the red blood cell mass.
So even though the amount of red blood cells
is increasing, the concentration
of red blood cells in the blood is decreasing.
Does that make sense?
So that's the first thing.
And it's called a
physiologic anemia,
because it's a part of normal pregnancy physiology.
Now, another thing that can happen
is a true anemia, or a pathological process,
not a physiological process, but
a pathological process, in which there is
an actual decrease in the number of red blood cells.
So here we're not talking about concentration,
we're talking about a decrease
in the actual number of red blood cells.
Most commonly, that anemia, the true anemia,
is due to a shortage of iron in the body.
So iron is used to make hemoglobin,
it's an essential part of hemoglobin, and
red blood cells are basically packets of hemoglobin.
So no iron means no red blood cells.
It's kind of like, if you're going to go make
chocolate chip cookies and you want to make,
let's say, 100 of them, and you have enough of
all of the ingredients to make 100 cookies,
but you only have enough chocolate chips
to make 80 cookies.
So guess what?
You're gonna end up
with only 80 chocolate chip cookies.
So why the shortage of iron?
Why is there a shortage of iron in pregnancy?
Well, these women, the pregnant women,
are by definition, women of reproductive age, right?
So they were probably menstruating before
becoming pregnant, and that blood loss
that occurs with each menstrual cycle claims
some of the body's iron stores.
So, that's one cause for
the iron shortage in pregnancy.
Another cause is that, in trying
to make it's own red blood cells,
the fetus claims some of mom's iron stores.
Now, iron deficiency is, by far, the most
common cause of anemia in pregnancy.
So much so, that if a woman is a pregnant woman
is found to be anemic, she is usually treated
with iron supplementation, and only if
that doesn't resolve the anemia,
if the supplementation doesn't resolve the anemia,
do we go looking for another cause.
So speaking of other causes,
it's worth mentioned that folic acid deficiency,
so, deficiency of folic acid, right?
can also, less commonly, cause anemia in pregnancy,
as can other causes, all the other
regular causes of anemia.
And something that happens particularly in
pregnancy is that the lifespan of a red blood cell
decreases, so the red blood cell doesn't quite
live to be 120-days old before dying,
and this further contributes to the anemia
that we tend to see in pregnancy.
So, I want to make the point that anemia
isn't a problem that's unique to pregnant women,
and you probably already know that,
but anemia does have some unique implications
in pregnancy that it doesn't have in other people.
For example, it can lead to things, such as,
a reduction in amniotic fluid levels in the fetus.
It can cause concerning fetal heart tones
or fetal heart tracings.
It can lead to spontaneous abortion,
low birth weight of the fetus,
and even death of the fetus, so it can be
a pretty serious problem in pregnancy.
Now, there's another important change that occurs
in the blood system of the mom during pregnancy,
and that is that pregnancy is a
hypercoagulable state,
so that is to say that the clotting mechanisms
in blood are running in overdrive during pregnancy,
so blood clots really easily, and this is primarily
because in pregnancy, there is an increase
in the production of clotting factors.
Factors such as thombrin and fibrinogen
and other clotting factors are made more.
And there is a lot of thought that perhaps this occurs
to protect the mother from excessive bleeding
during delivery, especially the bleeding that occurs
when the placenta separates from the uterus.
So maybe this is all meant to be protective?
The problem is, is that sometimes
you can have too much of a good thing,
and you end up with blood clots,
most commonly in the deep veins of the legs.
And some of that actually has to do with the fact
that the enlarging uterus puts pressure
on the inferior vena cava and the veins of the legs.
And that causes blood to pull in the lower extremities,
which is actually why pregnant ladies
almost always complain of swollen legs.
Anyways, this pooling of blood
in the legs can lead to blood clots,
and those blood clots are called
deep vein thrombosis.
Thrombosis just means clot.
So, in fact, the risk of having a deep vein thrombosis
is increased by five-fold in pregnancy and it's
important to know because the clot in the legs
can break off and it can travel to the lungs
leading to a pulmonary embolus,
in up to 40% of cases in which you have DVT,
which is dangerous and potentially fatal to the mom.
So, when the presence of a DVT or any clot
or thromboembolism, for that matter,
is confirmed, the woman is put on
anticoagulant therapy right away.
So those are just a couple of the
very important changes that occur
in the blood system of a pregnant woman.