Sonography of first Trimester Pregnancy - SD

Introduction

Hi, I'm Mark Cleaver.
I'm from the University of Wisconsin,
where I'm a professor of radiology.
Today I'm gonna talk about sonographic findings in first
trimester pregnancy, both abnormal and normal findings.
I'll take up the topic of sonography
of first trimester pregnancy in four different
subtopics, approach landmarks, signs
and abnormal early trimester pregnancy.

Approach to Diagnosis

First, with regard to the approach to diagnosis, there are,
as many of you know, who do ultrasound know,
there are two ways of looking at the
female pelvis,
both the transabdominal views and the endo vaginal views.
I believe that we should be using both
because in many ways they are importantly complimentary.
Endo vaginal views provide high resolution detail,
and these are the mainstay of diagnosis.
But transabdominal views are often indispensable
for seeing large or displaced abnormalities,
and also for getting a sense of how much
fluid is in the abdomen or pelvis.

Here's an example where this sort of
transabdominal view was critically important in diagnosis.
This is an endo vaginal view, of course,
and this is the outline of the uterus.
Inside the uterus, you'll see
that there's no intrauterine pregnancy within the
endometrial stripe,
and there is posterior to the uterus.
All this echogenic material, which
is somewhat amorphous from the transabdominal view.
It becomes quite obvious that here is the uterus
and that there is a large amount of blood
that is sitting right on top of the uterus
and creating that low level
and medium level echo pattern
that we saw on the earlier image.
This, which was difficult
to perceive from the endo vaginal view,
is quite obvious on the transabdominal.

The other thing that's important in the
approach to first trimester sonographic diagnosis is
putting this in the context of the beta HCG or the serum
or urine pro pregnancy test.
To remind you that there is a somewhat confusing
history to the beta HCG levels.
Most places now operate on the third international
reference preparation, and
so a positive test will be about a hundred milli
international units per milliliter.
As I was just saying, there is confusion.
There's a first, second, and third reference preparation.
I think most people do use the third at this point.
This gives some of the values by way of compare,
comparing these second and the third international standard.
The most important number in this chart
is this one right here,
and that is the level of the
beta HCG at which you should see a gestational sac,
and that should be about 2000.
And I'll talk a little bit about why
that's important when I talk about ectopic pregnancy.

So let's say you had no intrauterine pregnancy.
This is of course the uterus.
Again, the cervix would be over here,
no intrauterine pregnancy by endo vaginal imaging.
And the a CG level is less than the threshold at which we
would expect to see a gestational sac.
The differential diagnosis then would be the primary
consideration is that there's an early intrauterine
pregnancy before we can see it.
Atopic pregnancy, of course, has to be remain a possibility,
as does recent abortion or tumors,
but if you have no intrauterine pregnancy
by in vaginal imaging,
but the HCG level exceeds the threshold at which a
gestational sac is seen,
it should be seen here again, is the uterus.
There is the just the endometrial stripe.
If there is no intrauterine pregnancy at that point,
then ectopic pregnancy has to be the leading consideration.
The other thought possibility would be recent abortion, maybe a tumor
that elaborates HCG or false elevation of tests.
Remember that the a CG level, just like any test,
can have a certain number
of false positives and false negatives.
So if you have an a CG level, you can follow that over time,
and this is what they do.
The normal doubling time of the a CG is
about every second day.
If there has been embryonic death
or recent abortion, then the a CG level will decrease
abruptly if you have retained products or ectopic pregnancy.
The a CG level decreases slowly in some cases,
and in other cases of ectopic pregnancy,
the HCG level will increase more slowly
than would be expected with a normal intrauterine pregnancy.

Anatomic Landmarks

All right. We will talk next about landmarks,
certain anatomic landmarks that you would expect
to see at certain stages of development in the first trimester.
We'll talk a little bit about gestational sac,
the yolk sac embryonic pole,
and finally, some anatomic structures
that you should be able to see.

Gestational sac is the first sign of pregnancy is not
a specific sign.
However, what you often see is a little cystic structure
that is embedded within the decidua without any clear
identifier as an intrauterine pregnancy.
Indeed, some people have described small cysts within the
endometrium as evidence for ectopic pregnancy.
So this sign, though present is a somewhat nonspecific.

The first really specific sign
and a sign of considerable use is the so-called
double decidual sign.
Fundamentally, what is being seen here is that the decidua
on one side of the uterine cavity is separated from the
decidua that is surrounding the gestational sac.
So this would be the gestational sac here.
It's separated by the uterine cavity,
so this is the uterine cavity right there.
And so this, it is this crescent that you're trying to see,
you're trying to identify,
because that's what gets right
to these two epigenic arcs are this double decidua sign.
Here's an example of it.
This is an early intrauterine pregnancy.
You can see one decidua line here,
that's decidua capsis,
and another deci line here that's decidua prioris.
And this separating hypo coic arc,
or crescent is the uterine cavity itself.
So that's the double decidual sac sign
or the double decidual sign.
And this, of course, is the gestational sac right there.
From there are lookup tables
that correlate the gestational sac size
or the mean sac diameter to gestational ages.
It's the relationship is approximately
estimated by adding 30 to the mean sac diameter.
Of more importance is this number here.
Is that the mean sac diameter increases about a millimeter a
day for the first eight weeks,
and that's gonna be important number in determining how
what length of time you might choose
to follow up a case by ultrasound.

Here's an example of a mean sac diameter measurement.
It's a fairly crude measurement.
It's simply measuring the length and the width
and the transverse measurement and dividing by three.

The yolk sac is the first very specific structure of
identifiable structure within the gestational sac
and absolutely confirms an intrauterine pregnancy.
There are numbers that are correspond to
what is considered a normal yolk sack.
In general, the normal yolk sack should be less than
about six millimeters.
The number in literature is 5.6,
but realistically,
six millimeters is the number you should probably work from.
Here is an example of the yolk sack
and a twin pregnancy.
You can see two gestational sacks here,
and if you look very carefully right here,
and right here, you can see the thin membrane
that outlines the circular yolk sac.
Here to remind you,
the yolk sac is an extra amniotic structure.
This is the yolk sac here in this pregnancy,
and it is outside the amnion, which is shown here.
So this is the amnion.
The yo sacs is situated outside of
that in the choreo amniotic space.

So abnormalities of the yo sack, well, it can be too big
that is greater than six millimeters,
and it can be too small if it is thick, irregular, dense,
sometimes referred to as the calcified yolk sack.
That too is associated with embryonic death
and fetal anomalies.
Here is an example of a yolk sack that is too large.
Here's the embryonic pole right here,
and outside of the amnion is this very large yolk sac here
in measuring in excess
of six millimeters in an abnormal size.
Here's an example of the calcified yolk sac.
Here is the fetus.
Here, you can see from here to here,
and this is the oak sac to one side of it.
And you can tell right away that that is very genic
and small and of note,
you do not see a very distinctive shadow from this.
Nonetheless, this is you don't, you often do not see
that very weak shadow from it,
but that should not dissuade you from making the diagnosis.
Here's an example of a yolk sac that is
c granulated and irregular.

Next structure
that you'll see in early pregnancy is the embryonic pole.
The embryo is evident about the fifth menstrual weeks,
and you'll see in cardiac activity
by about five millimeters.
Now, this, in the literature,
the literature is somewhat variable on this point.
Five millimeters for a crown rump length.
To see a heartbeat is a very conservative limit.
In fact, you often see a heartbeat
before you even can discern an embryonic pole.
But certainly by three millimeters
and certainly no more than five millimeters.
You should certainly see a yoke tech
with modern i a heartbeat in the embryonic pole
with modern equipment.
Here's an example of a embryo that now is 18
millimeters of crown run length, which is well
above when we should expect to see the heartbeat.

Anatomic structures appear in certain predictable times.
Limb buds appear about eight weeks.
The mandible and maxilla appear about 10 weeks.
This is a quite a useful number
'cause if you have trouble making sense of some of the
fetal biometry, if you do see calcification of the jaw,
the mandible and maxilla, then you know the
fetus has got to be at least 10 weeks of age.
Here's some scanning electron micrographs
of the developing limb, bud.
It's I thought interesting.
You see that the fingers are sort of sculpted from the
early formation of the hand by a process of cell death
to produce these five fingers and five digits.
Here's an example of ossification
or calc ossification of the mandible and maxilla.
You'll see it right here. That's the mandible maxilla.
This is the fetal head here, fetal abdomen here.
And if you see os ossification of the me still in mandible,
you know that the fetus has got
to be at least 10 weeks gestation.
This is a staining of a fetus at 14 weeks.
And what's impressive about that is
that you go from some of the early ossification,
and in approximately a month, you get ossification
of nearly all the bones of the body.
Notice that there is ossification of all the
small bones of the hands
and the feet, as well as of course, the major bones
of the body.

A couple other anatomic structures of some usefulness
is therom cephalon,
which is visible about eight or 10 weeks.
This is an important structure to recognize
because if you're not familiar with it, it can look for
all the world, like a abnormal cyst
or even a defect within the fetal or embryonic skull,
but it is in fact a normal structure.
Midget herniation occurs between nine
and 11 weeks, so be very careful about making the diagnosis
of emale before about 12 or 14 weeks.
And then there's the FX in the Cho plexus,
which appear about nine or 10 weeks.
Here's an example of the developing feed embryonic brain,
the ro cephalon.
Notice how in this area here, the it looks as though the
embryo has a defect in the head.
This is the area of the head.
This, of course, is the body here,
and then there's this apparent large defect
that is the normal developing embryonic brain
and should not be mistaken for pathology.
Here's an example of midgut herniation into the base
of the cord right here.
This, of course, is the embryonic head.
This is the thorax,
and there is the herniation of the basal cord.
This, if this fails to retract back into the abdomen,
would constitute an infa seal,
but at this early stage,
it is not possible to tell the difference.
It, and the diagnosis really needs to be deferred
till 12 or 14 weeks.

Signs of Abnormality

Now, I'm gonna talk about a whole set of signs
that indicate abnormality in early pregnancy,
and then talk about how these are applied.
If you have a ultrasound scanner
that does not have an endo vaginal
or transvaginal probe,
if you see the gestational sac transabdominally, this is
by transabdominal scanning the mean sac.
Diameter should be visible,
or I should say the yolk sac should be visible at a mean
sac diameter of 20 millimeters or more,
and an embryo should be visible at a mean sac diameter
of 25 millimeters or more.
So those are useful indexes or rules of thumb.
If you have a scanner
that does have endo vaginal capability, then the numbers shift downward at a mean sac diameter
of eight millimeters.
You should see a yolk sac
and a mean sac diameter of 16 millimeters.
You should see an embryo.

Other signs, strong signs
of abnormality are a crown rump length of five millimeters
or more without a heartbeat or a very slow heart rate.
Heart rates below a hundred beats per minute are very bad.
Heartbeats
below 85 beats per minute are virtually always catastrophic.
There is a phenomenon known
as first trimester oligohydramnios.
Basically, this means that the crown, the embryo,
essentially fills the very small mean gestational sac.
There is actually a number that you could generate,
but most people just subjectively assess
how much fluid is around the embryo.
And then there is an important sign called the
empty amnio sign.
That is that the amnio is fully formed and apparent,
but no embryonic pole is evident.

Then there are signs of abnormality
that are somewhat less strong.
That is, there's a large, that is the large yolk sac,
which we mentioned, the calcified yolk sac
and the low HCG level for mean sac diameter.

Then there are signs of abnormality that I consider weaker.
These are weaker primarily
because they are less, they're more subjective
and more difficult
to identify an unusually large gestational sac
or a thin deci reaction.
These things are hard to judge the irregular margin of the
gestational sac or low implantation of the sac
unless that sac is in the cervix.
And then that's a very strong sign of impending abortion.

Abnormal First Trimester Pregnancies

So how do we apply these signs for diagnosis?
We'll take up several topics
of abnormal first trimester pregnancy, blighted ovum,
embryonic death, abortion, ex chorionic fluid collection,
gestational trophoblastic disease, ectopic pregnancy.

Blighted Ovum

Bliden OV is also called an embryonic pregnancy.
Basically what has happened is that the gestational
development is arrested before the embryo forms.
There's a large, what you will see
by ultrasound is a large empty gestational sac,
and the differential diagnosis would be early IPE
or pseudo gestational sac of ectopic.
This is what it looks like, the large empty gestational sac,
and this is where those numbers about when you should see a
yolk sack or an embryonic pole become important.
Since this is an endo vaginal scan, we would expect
to see the yolk sack at eight millimeters
and an embryonic pole at a mean sac diameter
of 16 millimeters.
So this is the large empty gestational sack here.
So, as I just said, you need
to compare the mean sac diameter to the presence
or absence of the oak sac or an embryo.
This is also where the empty amnion sign becomes important,
because if you see a formed amnion
and know embryonic pole, then that's the sign of
a arrested development of the pregnancy.
Then there's a, then you can also look for discrepancies
between sac size and HCG level,
and then there's an abnormal appearance of the sac.
And this, these are those, some of those signs
that are somewhat more difficult to apply.
Weak residual reaction, irregular sha sac shape.
Here's an example of the empty amnion sign, large
gestational sac demonstrated here,
and then there's the amnion fully formed.
You can see it as a thin membrane, a fully formed amnion,
but no embryonic pole.
And in that case, you can be certain
that this is an evidence of a blighted ovum.

Embryonic Death

Embryonic death is the embryonic death is
defined as the absence of cardiac activity.
When an embryonic pole is visible by transabdominal
or when the embryonic pole is visible,
but greater than five millimeters
and shows no cardiac activity.
The inverse of that is also important,
that if you have a crown rum length
of less than five millimeters
and you see no cardiac activity,
then follow up ultrasound is indicated.
Here's an example of embryonic death.
You can see early on the gestational sac here is somewhat irregular.
The embryonic pole demonstrated here
is you have loss of the normal segmentation
of the embryonic pole.
This is somewhat masturbated.
Usually by this time, you can see the head
clearly separate from the body demonstrated here,
and that usually those are seen as two identifiable segments here.
They they are somewhat amorphous.
Here's another example of embryonic death,
and this is a good example of the so-called first
trimester oligohydramnios.
You see that the embryonic the embryo virtually fills the entire
of the gestational sac here,
and there's very little fluid in this area
relative to the size of the embryo.
Here's another case of embryonic death,
or in this case, missed abortion,
which is the same thing.
You can see. Here's the embryo right here
in this case, this is farther along.
You can see most of the bones are ossified,
but they are now collapsed in on themselves.
There's very little fluid around the embryo
and the fetus has become more macerated
and is starting to resorb abortion.

Abortion

In most cases. When we're talking about abortion,
we're talking about spontaneous abortions,
but of course, there's also therapeutic
and missed abortions.
Missed. Abortion refers to intrauterine fetal demise.
This is largely a clinical diagnosis,
but there are ultrasound findings that can help you.
If you see a gestational sac
that is extended into the cervix, that is a strong sign
of an abortion and progress.
Sometimes a deformed sac or embryo is evident,
and almost always these embryos are without
cardiac activity.
This is an example of an abortion in progress.
This is the vagina here.
This, of course, is the urinary bladder.
This is the cervix,
and this would be the external laws there.
And you can see there's the gestational sac,
well within the cervix outlined here, uterus back here,
well within the cervix in this patient
with an abortion in progress.
What are some of the other findings
that might portend spontaneous abortion, of course, the thickened
or calcified yolk sac.
Sometimes you'll see an intrauterine mass
with cystic spaces, which
it represents the hydro degeneration
of the residual placenta.
Sometimes you'll see just an empty uterine cavity,
and then of course, the beta CG levels
should decrease abruptly.
Here's an example of hydrolic degeneration of the placenta.
Here is the area of the placenta right here,
and you can see that these,
there are multiple cystic structures within it,
as this placenta has already started to degenerate.

Extra Chorionic Fluid Collections

Extra chorionic fluid collections.
There are two important things that you need
to distinguish from sub chorionic hemorrhage.
One is the cho amniotic separation, which is a normal part
of development, and the blighted twin ovum from the
subchorionic hemorrhage, which is something akin
to abruption.
In this setting of cho amniotic separation,
the amnio amnion crosses in front of the placenta
and is evident until the 12th
or 16th week menstrual weeks of gesta of gestation.
In the case of sub chorionic hemorrhage,
almost always the fluid collection is contiguous
with the placental edge into one side.
Here's an example of a sub chorionic bleed.
Here is the air. Here's the placenta.
This, of course is the embryo here,
but you can see here that a margin
of the placenta has been lifted up.
And then there's all this low level echoes in this fluid
collection to one side,
and that is blood in this case of subc chorionic hemorrhage.
Now, one caveat about making that diagnosis is
that in normal pregnancy, if you are, if you see the amnion
here, here until that amnion
is contiguous with the choon, which is gonna be back here,
you'll have a space, it's called the chorio amniotic space
here, and at most gain settings at which we scan,
this looks koic.
If, however, you were to turn up the gain level,
and here I have done it to an unreasonable degree
that the gain level is way up,
you will actually see low level echoes within this chorio
amniotic space, and that is normal.
There's a jelly-like substance that fills this
space, and it will give a low level echoes normally.
So do not mistake that for subc chorionic hemorrhage.

Gestational Trophoblastic Disease

Then the issue of gestational trophoblastic disease,
the most common form that you'll see is the so-called
classic or complete mole or high deform mole.
In this case, fetal tissue is absent
and you'll get a degenerating placenta
with hydric villi and trophoblastic proliferation.
About 10 or 15 to 25% of these will go on
to develop malignant sequelae in the form
of either invasive mole or choriocarcinoma.
What does the molar pregnancy look like?
Well, it is somewhat variable in appearance
in the first trimester.
It can be echogenic or hypoechoic.
In the second trimester, we tend
to get the expansile echogenic mass
with multiple cystic spaces.
This is the classic form that you'll read about most often
and is sometimes compared to a snowstorm
or a Swiss cheese appearance.
This is the classic molar pregnancy of the second trimester.
Here it is, you can see an expansile mass within the uterus
with multiple cystic spaces shown here, here,
here within it.
And here's another example of the same pregnancy, expansile,
uterine mass here with multiple cystic spaces.
This is even a more florid example.
Here is the very large uterine mass occupying the entire
of the uterus with multiple cystic spaces shown here
and here and here, and multiple cystic spaces throughout.
Often seen in conjunction with these molar pregnancies is
a abundance of cyst within the ovaries,
the so-called fecal lutian cysts.
You see those in approximately 50% of cases,
and they are basically by ultrasound, large multilocular,
bilateral cysts.
And here's a couple of examples.
In a molar pregnancy, you can see that the ovaries
contain multiple large cysts on both sides.
And here's the one on the other side.
If the molar pregnancy is they evacuated,
and yet the beta a CG level rises
or does not return to normal within 12 weeks,
then the assumption is that the woman has an invasive mole.
In this case, the molar pregnancy has
infiltrated into the myometrium
and is still remains within the uterus.
The with single agent chemotherapy,
the cure rate is very high, nearly a hundred percent.
So this is not quite catastrophic,
but something that needs to be searched for.
Once you have metastases,
however, then you are in the category of choriocarcinoma.
The metastasis could spread to the lung, the vagina,
the liver, or the brain.
The statistic usually given about these molar
pregnancies is about half of them
of chorio carcinomas arise from molar pregnancy,
and the other half arise in a different setting,
possibly atopic or abortion.

There is the phenomenon
of a coexistent molar pregnancy and a fetus.
This is very uncommon,
and one assumption is that this is,
it represents molar transformation of one of the twin pregnancies, often included in discussion
of molar pregnancy is the soc so-called partial
or incomplete mole.
This is a somewhat unfortunate name
because what is really happening here is that you have
a triploid karyotype that this is an example
of aneuploidy.
In other words, you have three sets
of chromosomes in each cell,
and the three sets of chromosomes usually are accounted
for because two sperm fertilize a single egg.
There is the case of Divia,
where you could have a single egg that is fertilized
by a single sperm,
but the egg is in the process of division, so you can get
triploid in that way,
but almost all of them result from tr uh, d sperm.
The trophoblastic changes are more focal, embryonic
or fetal tissue is present,
and there should be no trophoblastic proliferation,
as you would see with a complete r true mole.
Then there is no essentially node malignant potential
associated with this entity.
This is an example of a triploid pregnancy.
This is the fetus here,
and you can see that the fetus is dwarfed
by this very large, massively large placenta with all these little cystic spaces within it.
So this is characteristic of triploid pregnancy,
very small growth restricted fetus, a very large placenta
with multiple cystic spaces.

So if you are if you see a woman
with a positive pregnancy test
and a cystic molar appearance within the uterus,
this is the differential diagnosis you should consider.
It could be a molar pregnancy,
it could be a triploid pregnancy or partial mole.
It could be hydrolic degeneration of the placenta.
And in a in a in the case
of intrauterine fetal demise, it could be retained products
of conception, and occasionally you'll get degenerating omas
that can look very similar to this.
Here's an example of these things.
This is the example of a uterus here, again,
by endo vaginal imaging.
And here within the uterus is this cystic expense I mass.
And this is a case of a partial mole
or a triple triploid pregnancy.
Here's a very similar appearing case.
This, of course, is the uterus here.
This is the expansile cystic mass,
and this is a case of a degenerating Oma.
Here's a case a case very similar in appearance.
Here's the uterus again here and here,
and here's the echogenic expansile mass
with multiple cystic spaces,
and this is a case of a complete molar pregnancy.
And finally, this is the last case, very similar
to the one just seen large expansile, uterine mass,
multiple cystic spaces, and this two is a complete mold.

Ectopic Pregnancy

A final topic I'll take up in this lecture is that
of ectopic pregnancy.
Ectopic pregnancies are more common than they have been in the past.
Almost all of them are tubal in location,
but they aren't exclusively tubal.
They can you can also have abdominal pregnancies,
ovarian ectopics, and cervical ectopics,
but these are quite rare.
There are many risk factors associated
with ectopic pregnancy, importantly, infection,
pelvic infection, prior ectopic,
or history of some sort of pelvic surgery.
Here is a drawing of ectopic pregnancy.
As is said, almost all of them are tubal pregnancies.
That is, the pregnancy is lodged in the tube as it is here,
but they can also occur in the cervix
demonstrated there, or in the ovary demonstrated here.
Even more rarely, the ectopic pregnancy can be
outside the gu tract and be abdominal
and abdominal pregnancy.

There's an important subset
of tubal pregnancies called corneal
or interstitial ectopics,
and that's when the ectopic pregnancy is larged at the
cornua of the uterus.
So there are specific ultrasound findings in the di in the
assessment of ectopic pregnancy.
There is of course, the unruptured ecto live ectopic
that you can see in the adnexa,
or you could see an intrauterine pregnancy, which
virtually excludes the possibility of a coexistent ectopic.
The odds against having both a intrauterine
and an extrauterine pregnancy are very small,
except in patients
who are undergoing ovarian ovulation induction
or infertility treatment.
Here's an example of an ectopic tubal pregnancy.
This is the uterus transabdominally.
We're looking through the urinary bladder here,
and right here is the ectopic pregnancy seen out in the left aa.
Here's an example of a corneal pregnancy.
These can be difficult to diagnose,
but what's important about them is
that they are always very eccentric in the uterus.
This is the contours of the uterus here.
This, of course, is the endometrial stripe.
The other thing that's important about them is
that there's very little myometrium laterally,
and the endometrial stripe ends
directly onto the gestational sec
that's called the interstitial line sign.
Remembering that the endometrium
or the uterine cavity would wrap
around the gestational sac normally,
and that would produce the double residual sign.
So here's an example of why that happens.
The endometrium comes right up against the u,
the uterine, the endometrium homes right onto ending in
in a blunt t junction onto the gestational sac.
Here's an example of an ectopic pregnancy that is
so abnormal that is actually quite easy to miss mistake.
This is a transabdominal scan
through the urinary bladder here.
This is the uterus outlined here,
and the gestational sac is clearly extra uterine,
and in fact is outside the gu tract altogether.
This is an abdominal pregnancy.
What's important about this diagnosis is the identification
of the uterine cervix.
So the o the way you would diagnose this is
that you identify the uterine cervix
and follow the endocervical canal up into the
Uterus, and that will show you that this is
outside the uterus and not within it.
So it's very important to always locate the cervix
and be very clear
how the endocervical canal joins the endometrial cavity.
Here's an example of an ectopic pregnancy in the left aa.
This is the area of the uterus here.
This is the broad ligament.
This is the left ovary over in here in this area,
and here's the ectopic pregnancy right there.
What's important about this is notice
that the tubal pregnancy in this case
has an echogenic ring around it.
This is the so-called ad adnexal ring sign,
which I'll talk about in a minute,
and is very useful, the exception
to the intrauterine pregnancy rule.
That is, that it's very unlikely to have both.
The intrauterine and extrauterine pregnancy is the so-called
heterotopic pregnancy seen almost exclusively in the setting
of ovarian induction or infertility treatments.
Here's an example of scanning into the right adex,
and you can see one gestational sac here, here,
and then if you scan over the uterus demonstrated there,
you can see that there is an intrauterine pregnancy as well.
So this is called heterotopic pregnancy,
and it does occur rarely again
because this woman in this particular case
was undergoing ovarian induction.
She had not just one intrauterine sac,
but two, there's one two as well
as the ectopic pregnancy.
Notice that in the posterior cul-de-sac, there's a lot
of fluid here with low level echoes constituting blood.
If you look up high into the flanks, you'll notice
that there's blood also in the hepa renal space, indicating
that this woman has quite a lot
of blood in her abdomen and pelvis.

So there are strong
but not specific ultrasound findings of
ectopic pregnancy.
One of the most important is the so-called adnexal ring sign
or tubal ring sign.
This is very important
because the positive predictive value is very high in the setting
of a positive pregnancy test,
and no intrauterine pregnancy, I should say
that corpus luteal cyst can sometimes look like this,
but in that case, you should not.
The woman in most cases would not be pregnant.
The reason why you have the tubal ring sign
or the adnexal ring sign is
that the echogenic bl tissue lines the tube,
and as you cut across that tube, then you'll get this sort
of round genic donut.
There's a large amount the other signs
of ectopic pregnancy or a large amount of fluid.
By, and by fluid I mean blood within the
abdomen or pelvis.
And in many cases, you'll see the low level echoes
indicating that it is complicated fluid, not simple ascites.
Here's an example of the adnexal ring sign.
Here, you can see this very echogenic ring
that surrounds the gestational sac here out in the ad nexa.
So if it's setting of a positive pregnancy test,
no intrauterine pregnancy, this is a very potent sign.
Here's an example of free fluid.
In this case, you see a relatively small amount
of fluid here in the posterior cul-de-sac,
but it does have low level echoes,
but there is an abundance of fluid up in the upper abdomen.
So to remind you
and to warn you that the woman can have a lot of blood in
the abdomen that is localized superiorly
in the abdomen and will not be evident necessarily.
If you look only at the pelvis, other signs
of ectopic pregnancy complex adnexal masses,
the positive predictive value of that
sign is actually less than that of fluid.
And the reason for that is that there are so many reasons
that young women might have complex adnexal masses,
including tub, ovarian abscesses, endometriomas,
ovarian masses or dermoids.
But if you have the combination of adnexal masses
and free fluid in the positive,
pre dictive value in this,
in the proper setting is quite high.

Occasionally you'll see a reference to the residual cast
or the pseudo gestational sac of pregnancy.
And this the pseudo gestational sac occurs in the setting
of ectopic pregnancy
and represents a sloughing
of the decidua into the uterine cavity.
Here is an example of that.
Here is the ectopic pregnancy here out in the adnexa
and within the uterus demonstrated.
There you have a small amount of fluid that could be
feasibly mistaken for a gestational sac,
but simply represents a sloughing
of the decidua within the uterine cavity.
Importantly, you will not see the double
decidual sign in this setting.
Remember that the finding of a having a normal pelvic study does not eliminate the possibility
of ectopic pregnancy the presence.
Clearly, some five to 30% of women
with ectopic pregnancies will have a completely normal
appearing ultrasound study.
Some people have advocated the use
of doppler ultrasound in the diagnosis.
I personally have found this of limited usefulness,
but the claim
is that you will see low resistance blood flow in the area of the ectopic pregnancy.
This is an example of this low impedance flow characterized
by a high end diastolic velocity,
and remind you that ectopic pregnancy is diagnosed both
by ultrasound and by other factors.
So if you have a serial beta HCG level
and it does not increase as much as 63%,
or the doubling time is somewhat less than every two days,
then the possibility
of ectopic pregnancy must be considered very seriously.

Summary

So in summary, something is very wrong
in the first trimester.
If you find these signs, these are the signs to
that are most important.
If you have a mean sac diameter that is eight millimeters
or larger, and you do not see a yolk sac
by transvaginal imaging, if you have a mean sac diameter
of 16 millimeters or greater
and you don't see an embryo,
if you see a fully formed amnion,
but no embryonic pole,
if you do see a heart rate within the embryo,
but the heart rate is less than a hundred
and some people say less than 85, then the chances
of a viable pregnancy is much less.
If you see a thick or calcified yolk sac,
if you see evidence of first trimester oligohydramnios
or very little fluid around the developing embryo,
if you have no cardiac activity in the crown,
rump length is five millimeters
or greater, the chances
of having a viable pregnancy are vanishingly small.
And finally, if you have a positive V-D-H-C-G
and no intrauterine pregnancy is evident
by transvaginal imaging, especially if
that HCG level is 2000 million international units
or greater, then the possibility
of ectopic pregnancy becomes very high
and something to be considered seriously.

So that is a kind of overview of first trimester pregnancy.
We talked about the approach to diagnosis,
some normal landmarks that you would expect
to see at predictable times.
I categorize certain signs as very strong, less strong
and weaker signs of abnormality.
And then we talked about how these signs can be applied
to sonographic images in the diagnosis of specific
abnormalities of first trimester pregnancy.
Thank you.