"The Standard Antepartum Obstetrical Sonogram" AIUM Guidelines Revisited - SD

Introduction

Hello, I am Ruth Goldstein.

I'm chief of ultrasound at UCSF, University of California, San Francisco.

Today we're gonna talk about the standard obstetrical sonogram, how the AIUM guidelines can help you do a good job and stay out of trouble.

Today we're gonna talk about the standard obstetrical sonogram and the AIUM guidelines.

And this lecture should also be entitled How to Do a Good Job and Stay Outta Trouble.

Should We Do Routine OB Ultrasound?

The first question when you talk about standard obstetric sonography is usually, should we be doing OB ultrasound as a matter of routine during pregnancy?

And to answer this question, the NIH Consensus Conference convened in 1984 in the American College of Obstetrics and Gynecology again in 1988, and all agreed that OB ultrasound should be done for only very specific indications.

Of course, they produced a list of these potential indications that were extremely long and included just about anything you could think of as an indication for an obstetrical sonogram.

And truth be told, in the year 2008, the majority of pregnant patients who get prenatal care in the United States get at least one sonogram during their pregnancy, and many get two or three.

AIUM Guidelines for Performance

So we'd like to talk about the guidelines for performance of the standard obstetrical sonogram.

And these were, these are practice guidelines that were first published in 1996 and have undergone multiple revisions, the last one of which has been published in October of 2007.

And I've listed the URL for you in case you would like to reference this.

Importantly, they described these guidelines as a reflection of what the AIUM, the American Institute of Ultrasound in Medicine considers the minimum criteria for a complete examination, but they're not intended to establish a legal standard of care.

So what these guidelines offer us is one, a standardized protocol, which helps us perform complete and accurate study.

And they also establish reasonable expectations both for the patients who undergo these examinations and also for the referring doctors.

And I have to say, it or not, these guidelines represent the groundwork for the quote unquote standard of care, especially in the United States.

And these guidelines are invoked in almost every legal case in which someone feels that the proper standards have not been followed.

Standard Obstetrical Sonogram Overview

So let's talk about this standard obstetrical sonogram.

And just briefly, we call this in our lab the level one examination, and that's distinguished from the targeted sonogram in our lab called the Level two examination, which requires considerable additional effort to the standard obstetrical sonogram.

The targeted exam is really tailored to risk, elevated alpha-fetoprotein and abnormal outside sonogram with a certain finding, a history of diabetes in pregnancy, drug exposure, et cetera.

And because it is tailored to a specific risk, it is not a standardized exam.

And that is an important distinction from the standard OB sonogram, which for all intents and purposes, really should be the same for every patient.

First Trimester Guidelines

So the guidelines are as expected different in the first and second and third trimesters in the first trimester.

Very clearly stated is our obligation is to identify the appropriate and true location of the gestational sac to confirm the presence or absence of embryonic life, to measure the size of the embryo and the crown rump length measurement to determine the number of fetuses or embryos.

And finally, to look carefully at the uterus, including the cervix and the adnexa.

And transabdominal imaging in the first trimester, in my view, is sufficient as is written in the guidelines.

Vaginal imaging is only PRN or as needed.

Location of Gestational Sac, Uterus, and Adnexa

I'd like to just talk for a moment about the location of the gestational sac and the uterus and adnexa.

Of course, the cervix imaging is not all that terribly important in the first trimester, but it is important because it ensures that you have connected the central uterine cavity to the cervix.

And in this way, you can show that the gestational sac, as you see on your right here, is connected to the cervix.

It is the central uterine cavity.

And I like to remind people that the cervix should be imaged so that you don't make the kind of mistake that was made in this image in which a perfectly normal looking embryo with a heartbeat was identified on vaginal scanning.

But the person who did this, and granted it was late at night, and they the patient was from the emergency department, they pretty much just wanted to get the exam over with, failed to recognize that there was an empty uterus adjacent to this gestational sac.

And this represents an ectopic pregnancy.

So the cervix is included at just as a nice little reminder that you have to connect the central uterine cavity or the place where the gestation is located to the cervix to confirm its intrauterine location.

Presence or Absence of Embryonic Life

The presence or absence of embryonic life is an important one and of course, heart motion is the best evidence of life in the first trimester.

And this is a real time diagnosis.

You can see the heartbeat in the first trimester embryo.

I believe that we should only do vaginal scanning if it is necessary to see the embryonic heart motion.

And I don't believe that doppler nor m mode are necessary for making this diagnosis.

I think it's simply a matter of observing it.

We document it in cine clip, which is very, very helpful.

And the communication with the sonographer that the heart motion was evident is an important thing.

Before we used to store cine clip, before we had the capability of storing cine clip, we used to have our sonographers write positive embryonic heart motion on the image.

In most cases, heart motion is detected as soon as you can see the embryo.

And as you see in this image, it can sometimes actually be seen before there's a measurable embryo.

But it may not be visible before the embryo reaches five millimeters in size.

And this is why the caveat of the size caveat is included.

Don't diagnose a demise of the embryo until the crown rump length gets to be five millimeters.

And this is included mainly to ensure that you don't call a normal pregnancy abnormal just based on the absence of heart motion, based on a very tiny, almost indiscernible embryo wait till it reaches a size of five millimeters before you call it a failed pregnancy.

Crown Rump Length

The crown rump length, this is really the mainstay of gestational age assessment in the first trimester.

We're quite accurate.

We can usually estimate gestational age within five days.

And this is using crown rump length measurement.

Actually, it's best between six and 12 weeks or so.

When you get into the 13, 14 week, you're kind of in that gray zone between measuring actual head circumference and biparietal diameter compared with a crown rump length.

If your main goal in performing obstetrical sonography is to determine gestational age, then this is the time you wanna do it.

However, if you're only gonna perform one sonogram during gestation, because you get so little morphologic information and as we'll talk about, you will get almost as good dating information a little bit later on, this is probably not the greatest time to do a gestational age assessment in the first trimester.

Nuchal Region

In 2007, the guidelines have an additional comment about the nuchal region and this region can be abnormally thickened in association with chromosomal abnormalities.

And the guidelines indicate if possible, the nuchal region should be assessed as part of a first trimester scan.

And that is merely to get you to notice if the nuchal area is abnormally thickened.

And I think any nuchal fold area, and this is not written in the guidelines, but it's my opinion that any nuchal fold area greater than about two and a half millimeters should probably be referred to a nuchal translucency screening program.

And I want to emphasize that individual aneuploidy risk, an individual woman's aneuploidy risk for a particular pregnancy is best determined by nuchal translucency screening programs, which are very stringently quality controlled, and very careful measurements are correlated with the crown rump length.

And an individual risk can be offered to the woman in the standard obstetrical sonogram, the one that's performed for dating, or that's performed for vaginal bleeding.

You will not make an individual aneuploidy risk based on the nuchal appearance.

Fetal or Embryonic Number

Now, the fetal or embryonic number is another important part of this examination.

As you know, twins are all considered to be high risk pregnancies, but some are higher than others.

And not only is important to report the number of embryos, this is obviously a very important thing to the parents to know if they're having twins or triplets or whatever.

But the chorionicity is absolutely critical to be both observed and reported in the first trimester.

And that would be done on the basis of either a thick intervening membrane, which is the chorionic membrane versus no thick intervening membrane, which would be a monochorionic twin gestation.

As you know, chorionicity moreover than the number of fetuses are in there, chorionicity is much more important than knowing whether there are just twins or triplets.

So, very important thing to do, let me just go back to that for a moment.

I would say definitely take the opportunity.

Complications can arise from monochorionic pregnancies later in gestation, and it is absolutely critical when you talk about how you may manage these problems, including twin twin transfusion or selective intrauterine growth restriction or even an anomaly based on the chorionicity.

We make our management decisions based on the chorionicity.

It's much easier to handle a dichorionic twin gestation with a problem in one than it is a monochorionic due to the shared blood supply.

Second and Third Trimester Guidelines

So in the second and third trimester, the guidelines, the inclusions in the guidelines are expanded somewhat for obvious reasons.

Now we're gonna talk about not only fetal life number and presentation, but amniotic fluid volume becomes important, the location of the placenta relative to the cervix, the estimation of gestational age and growth and weight, probably the cornerstone of the standard obstetrical sonogram, the uterus and adnexa, again, important as part of this examination and the specified fetal anatomic survey, we will take these in turn.

Let me also say that in the United States, of course, we are required to store a permanent record of our images with the date, the name or identifier, a written report in the medical records.

And all of this are according to the American College of Radiology Communication standards.

Amniotic Fluid Volume

Amniotic fluid volume can be assessed both subjectively more qualitatively as well as using semi-quantitative methods.

The semi-quantitative methods would include deepest vertical pocket or the amniotic fluid index of late.

The amniotic fluid index, particularly in singletons, has become very popular, and it's quite easy to do.

The uterus is simply divided into four quadrants, and the deepest pocket in each quadrant is measured in centimeters.

Those are summed, and the total is the amniotic fluid index.

And there is some variation with gestational age, but as a general rule, normal is considered somewhere between five and 20 or 24 centimeters depending on what you if you like to be specific or sensitive.

And I can't emphasize enough that the amniotic fluid index, while it is a number and we do make a numeric or quantitative assessment of the fluid, it is really not a precise number.

And the most important part of the recommendation to assess amniotic fluid volume is that the extremes of amniotic fluid volume are associated with poor outcomes.

So it's really the extremes when you get into the over 20 centimeters for amniotic fluid in less than five centimeters, that you're gonna be looking for the causes and potential association with problems in pregnancy that can be managed and intervened upon.

Polyhydramnios is usually not a very subtle diagnosis.

Basically, you've got the fetus swimming in a sea of amniotic fluid, subjectively, if the abdominal wall doesn't fill the uterus in the AP dimension, you're kind of suspicious there may be polyhydramnios.

But usually if you have severe polyhydramnios, it's not difficult to diagnose.

And of course, we've looked at this number of ways and have determined that the greater the polyhydramnios, the greater the risk of a fetal anomaly.

So if you see something like this, you would be thinking of twin twin transfusion with a monochorionic pair and one with polyhydramnios, the other with oligohydramnios, you might be thinking of high gut obstructions such as esophageal or duodenal atresia.

And finally, anything with over perfusion, sacrococcygeal teratomas or things like that, severe central nervous system anomalies can sometimes produce very severe polyhydramnios.

But in today's practice, most commonly, those are diagnosed earlier before polyhydramnios develops.

And in these cases, if you see polyhydramnios, I think that's a very good indication for what we call the level two obstetrical sonogram or the targeted obstetrical sonogram.

Similarly, too little fluid known as oligohydramnios is bad for two reasons.

One is it's bad for fetal development for the lungs to develop.

You need adequate amniotic fluid for the limbs to develop without contractures, you need adequate amniotic fluid.

But perhaps more importantly, from a diagnostic perspective, oligohydramnios may be the first suggestion that there is a fetal anomaly.

And that will lead you to look more carefully at the fetus.

And because basically the differential when you see severe oligohydramnios is that she's ruptured her membrane.

She has premature rupture membranes that there is a dysmaturity syndrome, such as post dates or intrauterine growth restriction going on, or finally, and most importantly, that there is a GU or genitourinary malformation.

And for this, I would go directly to the fetal urinary bladder.

If there's oligohydramnios and the fetal urinary bladder is large as it is in this particular case, there isn't any fluid anywhere in this uterus except for the fetal urinary bladder.

And of course, you would be thinking of bladder outlet obstruction.

And in this case, with the typical keyhole appearance, you would make the diagnosis of posterior urethral valves.

If you go to the bladder after you've made the initial diagnosis of oligohydramnios, and you see the two umbilical arteries coursing around the urinary bladder, but there's no fluid in the urinary bladder, then you're talking about bilateral renal disease, most likely.

And you look carefully in the renal area, if you see a picture like this, you will make the final diagnosis of multicystic dysplastic kidneys, which in this case are bilateral.

Of course, in order to have oligohydramnios and an empty bladder caused by a renal abnormality, it must be bilateral, okay?

A unilateral multicystic dysplastic kidney and a normal kidney will not produce oligohydramnios, and they will not produce an absent urinary bladder.

A unilateral multicystic dysplastic kidney and contralateral renal agenesis, which is a much harder diagnosis, will cause absent urinary bladder and oligohydramnios.

So it's very important once you see an absent bladder, an oligohydramnios to look up in the flanks and see if you can make the diagnosis regardless.

In the second trimester, if you have absent urinary bladder and severe oligohydramnios, the prognosis is extremely, extremely poor.

Placental Location

The placental location in its relationship to the cervix is a key part of the standard obstetrical sonogram.

In fact, placenta previa has got to be one of the most important causes of maternal and fetal death in the developing world.

And this is a very important part of our diagnoses in the even in the developed world.

And for this, we must, one, be able to identify the placenta, and two, identify the edge of the placenta as it relates to the internal cervical os, as well as the ipsilateral cervix and contralateral cervix.

And what you want to become familiar with is the position of the cervix at the first turn of the urinary bladder and its relationship to the edge of the placenta.

This is not that uncommon of an image and what this represent in pregnancy, for whatever reason, what this represents is a typical false positive diagnosis of placenta previa.

So here you see the placenta for all intents and purposes.

This very much looks like the cervix here, but it's not really at the first turn of the urinary bladder.

But you see if you look carefully at this, you can appreciate that these are lower uterine segment contractions, and in fact, the cervix is way down here.

So let's just look at that one more time because this is a very common phenomenon.

In the second trimester of pregnancy, you get these Braxton Hicks or kissing contractions as we call them, and for whatever reason, they're really trying to fool you.

They contract and oppose each other, simulating the endocervix as you see here.

But be aware and be very careful about finding the true cervix.

If you're getting a measurement on the cervix of five or six or eight centimeters, you know that no normal woman has a cervix measuring eight centimeters.

So be aware that it may be elongated, and you may be dealing with lower uterine segment contractions.

And the more you're aware of that, the more it becomes clear what the anatomy of the cervix is.

And you can see it very nicely here.

The first turn of the bladder, the cervix here, here is, here are the lower uterine segment contractions.

This cannot be a placenta previa because as these resolve, this placenta is gonna go right like this.

And if it truly were attached to the cervix, you couldn't get a contraction between the placenta and the endocervix.

Estimation of Gestational Age, Fetal Growth, and Weight

The cornerstone of the standard obstetrical sonogram, as mentioned, is pretty much the estimation of gestational age fetal growth and weight.

And for this purpose, we measure certain parts of the fetus, the biparietal diameter, the head circumference, the abdominal circumference, and the femur length.

And we put these measurements into a regression equation, which emphasizes the head and femur length to produce a gestational age assessment.

And we use a slightly different regression equation to produce a fetal weight estimate.

That regression equation, the fetal weight regression equation, most heavily emphasizes the abdominal circumference.

So the same biometry is used in both equations, but one, in the case of the gestational age assessment, the femur length and head size are most heavily emphasized.

And in the fetal weight equation, the abdominal circumference is most heavily emphasized.

And the reason for that is that when you look at the correlates of weight and size, it turns out abdominal girth most closely correlates with fetal weight.

For the biparietal diameter, we are gonna look for the third ventricle here and the thalami, and usually the cavum is included and we will measure outer to inner for the head circumference, as you know, we go all the way around the circumference of the cranial vault, not to include the thickened scalp.

If it is present in the femur, we wanna measure the osseous shaft of the femur and be cautious about not including the distal femoral epiphysis.

You can enhance the estimation of gestational age by two to three weeks by including this specular reflection off the distal femoral condyle.

The best way to measure the femoral length is to be in a plane perpendicular to the shaft of the femur.

Then, you know, and if you line that up and you actually see the two femoral condyles, the proximal and the distal femoral condyles, you can measure the bony shaft and the bony shaft alone.

The abdominal circumference should be obtained again in the outer circumferential way at the level of the stomach and the right portal vein, the right portal vein here, you see the right portal vein in the left portal vein.

This is the so-called hockey stick appearance.

That is the plane of section you want to include for your abdominal circumference.

And usually the machines will take your measurements and correlate with a nomogram in the machine, stored in the machine to a certain gestational age.

It takes that regression equation again and calculates the graphically, estimated gestational age and the estimated fetal weight.

You will put in the, based on the last menstrual period, the estimated due date based on her clinical dates.

And it will, the machine will take this measurement of estimated fetal weight in grams and compare it to the clinical age and give you a percentage.

And that is to say, if this fetus were truly 28 weeks, six days, and it weighed 1393 grams, what percentile would it lie in?

And the answer to that in this particular case is 55.

Now, the accuracy of predicting gestational age is pretty good throughout gestation, because two standard deviations is plus minus 8%.

But you see as you go farther in gestation, because the number of weeks that the baby is are greater than 8% becomes a larger error.

And that's why we usually teach that third trimester sonograms are not very good at estimating gestational age, whereas the crown rump length, which is a very small number of weeks, can estimate within about five days.

So technically speaking, crown rump length is the best way to estimate gestational age, but second trimester sonography between 14 and 21 weeks does a very good job as well.

And you can see 8% turns out to be within one to 1.5 weeks.

Therefore, if you are gonna do it at one, if you're gonna do one sonogram during gestation, you might as well do it in the 18 to 20 week period of time.

'Cause you're gonna see all of the important anatomy and you're not gonna really sacrifice much in the way of dating.

Okay, estimating fetal weight is good, but it's not quite as good as estimating gestational age.

And if we had to put a number on it, we would say instead of two standard deviations being plus or minus 8%, two standard deviations are now 15 to 20%.

And again, regression equations that calculate estimated fetal weight will emphasize the abdominal circumference.

So this is a technically important part of the standard obstetrical sonogram.

Let me just show you ways in which you can mismeasure the abdominal circumference.

Here's a textbook measurement of the abdominal circumference in the proper way, the hockey stick right portal vein the stomach.

Here's another one that was used as an abdominal circumference, but you see the stomach here, but instead of the hockey stick, you see an elongated left portal vein.

What is the difference in the measurement of this versus this?

Well, the answer to that is that this image increases the size of the abdominal circumference because instead of being axial through the abdomen as you would be if you saw a portal vein in this appearance, you are more angled through the abdomen.

And if you see any elongated portal vein, and therefore you would overestimate the size of the abdominal circumference.

Just a small technical issue that I wanted to remind you about in your measurements of the abdominal circumference.

Now, in the first 20 weeks, the size of the fetus pretty closely reflects gestational age.

And the rare exceptions to this are very severe early intrauterine growth restriction, which fortunately is rare.

And second, a chromosomal or severe fetal anomaly in which the fetus will be small for dates based on the anomaly.

But as a general rule, most of us grow pretty much the same in the first 20 weeks.

In the second half of gestation, the size of the fetus will reflect both the gestational age of the fetus as well as the growth pattern of the fetus and growth pattern.

I mean both the placental sufficiency or insufficiency, the environment of the fetus, and also constitutional issues so that if your both of your parents are six three, you would probably tend to be a little bit on the large side, large size in the third trimester compared to someone whose both parents were five feet or five foot two.

So the percentile becomes actually quite important in the second half of gestation, whereas it's not so important.

And sometimes it's hard to obtain in the first half of gestation because the charts really don't go down that low.

It takes a very big alteration in growth to demonstrate an alteration in the LMP centile, but that's not really the case in the second half of gestation, the second half of gestation, the centile according to the clinical dates becomes very important.

And this becomes more of a reflection of normal growth of the fetus as you see in this particular case.

It compares the generated weight of the fetus based on your fetal biometry to others of the same clinical age.

And this is a very important concept, so I'm gonna repeat it in a couple of different ways.

You look at nomograms of all fetuses of a similar clinical age, or some people call that LMP age and you say, how are they growing when they're 28 weeks or when they're 29 weeks or 31 weeks, say, okay, the 50th centile is around this, this weight, the 25th centile is around this weight.

The 70th centile is around this weight, and you compare it to nomograms, you compare your generated fetal size to those nomograms.

So look at a case like this, this is a nice example of what might happen to you in the interpretation of sonograms.

Here's a fetus who by dates or by quoted due date is supposed to be 33 weeks, but she's a little bit hesitant about her LMP, and you know, there's just a sufficient waffling where the sonographer might say, well, she's not really sure of her dates.

And we look at the fetal biometry that's obtained in this particular case, and we have a 2028 and 6 29 and 1 27 and two and 29.

And when you're thinking, geez, all of these are about four weeks less than her stated dates, maybe she's just a month off in her dates.

But this is a very important problem and one that I would strongly recommend you don't make.

If you see LMP centile less than the 10th centile, you should think of intrauterine growth restriction and resist changing menstrual dates.

This particular fetus is dying in utero.

This particular fetus is living in what they call a hostile intrauterine environment.

The placenta is not supporting this fetus's growth.

If you do not recognize that this fetus is chronically hypoxic and growing abnormally, this fetus will die in utero before it can be delivered.

On the contrary, if it is delivered early, it may suffer some of the effects of prematurity, but it will be alive and they will be able to nourish it much better out of the womb than in the womb.

This is a growth restricted fetus, a very sick baby.

Now the guidelines recommend if previous studies have been performed, appropriateness of growth should be reported, and this is a very important part of your job in the standard obstetrical sonogram.

If prior studies have been performed at your location at your institution, you need to compare your results to them.

I don't think it's necessary if the images are hard to find or whatever to necessarily look at every single picture that was taken in a prior exam.

But there should be a report that's available to you.

It should be clear what they used as her due date, what they used estimated gestational age, what the sonographic due date was, and you need to make a comment about the interval change from one study to the other.

I can't tell you how many lawyers have come to me to discuss this particular issue.

If prior studies have been done at your institution, you need to compare the current exam to the prior one.

And importantly, the pregnancy should not be redated after an accurate earlier scan has been performed and is available for comparison.

That means if an 11 week sonogram was done at your institution and they generated a due date, and she comes in and says, I can't remember when my last menstrual period was, but it was about, I do remember on my first sonogram that it was about three weeks discordant from what they found on the sonogram.

You must compare it to the first sonogram and you should never red date her based on the current sonogram.

So later sonograms are not as accurate at dating as earlier.

Sonograms are always use the earlier sonogram, and if the earlier sonogram is not available, always use her clinical dates.

She will always remember what she was told as her due date based on her first trimester, either physical exam or sonogram.

This was another very interesting example, and I think illustrative example of this point precisely.

This is a patient who was referred to us for a potential short limb dysplasia.

The patient was very, very anxious because the doctors at the outside site had told her that she may be having a dwarf.

And according to our information, she was 24 weeks based on an early sonogram.

But she said the early sonogram wasn't very good.

It was just done in her doctor's office.

And in fact, according to this, her femur length was 20 weeks, which was four weeks discordant with what she used as her stated dates.

But look at the rest of the fetal biometry.

20 weeks was the femur length, 20 weeks was the humeral length, but all of the other measurements were similarly smaller than her stated due date.

So the femur wasn't all that short compared to the abdomen and the head, but all of the measurements were very short compared to what her stated dates were.

Now, when she told me what her due date was, which was August 8th, she said that this was a generated due date.

She could never really remember her last menstrual period, no problem.

It was generated based on a six week sonogram in the doctor's office.

She said, well, he doesn't have very good equipment, which just sounds like someone scratching their nail on a chalkboard.

To me, a six week sonogram is great.

Regardless of how bad the equipment is, you would have to really make a mistake confusing a six week pregnancy with a nine week pregnancy based on a first trimester.

The difference in appearance between six weeks and nine weeks is the difference between a grain of sand and a blown up balloon.

It is very obvious and is unlikely regardless of how bad the end quote the equipment was for imaging in the first trimester.

It's very unlikely her doctor would've made this mistake.

So if we had based our conclusions on the biometry alone, first of all, we probably wouldn't have called a dwarf, but second of all, we would have missed the opportunity to make the diagnosis of very early and severe intrauterine growth restriction.

So my recommendation to you is there are three ways to always stay out of trouble.

One is always ask her LMP date. Okay?

It doesn't cost you anything to ask when her last menstrual period was.

If she doesn't remember it, which some don't ask her what they told her her due date was.

Women often forget when their last menstrual periods were, but they do not forget about their due date.

They've informed everybody, all their relatives, about when the baby is due.

And even if it's off by a day or two, they remember their due date.

And if she's had a prior sonogram at your center, you are really obligated to compare it.

The worst mistake is missing a growth disturbance because you change the dates or we're negligent in comparing your current sonogram with the first sonogram done at your institution.

And if all else fails and there's discrepancy in what her true dates are and what you think her dates are, simply report how you determine her due date.

This will allow the doctor who may glean additional information at a later time, her referring doctor to adjust the clinical percentile of her fetus at a later time and allow you to do it as well.

So you have relinquished responsibility for determining her due date as soon as you report how you determined her due date and it's available to the referring doctor.

Okay?

Fetal Anatomic Survey

The standard obstetrical sonogram also includes a very specified and thoughtful fetal anatomic survey with attention to important areas that are highly reflective of some of the commoner fetal anomalies.

And I've indicated the new inclusions in the guidelines in blue for you.

These are new since the year 2007, but you're probably familiar with most of these in the head.

You wanna look at the cerebellum, the choroid plexus, the cisterna magna, the lateral ventricles, the midline echo, which in some cases is the interhemispheric fissure.

In some cases the falx, the cavum septi pellucidi the lips.

Lips are a new inclusion and the lips are included, not because clefts represent life-threatening abnormalities, but they're often associated with other anomalies that can be better assessed at a later time.

And also it's very humane for the parents to know ahead of time if they are having a fetus or a child with a cleft lip or palate in the chest.

You wanna make sure that you get a four chamber image of the heart and a feasible outflow tracks.

I would strongly recommend those in the abdomen, the stomach, not just the presence but the size and the location of the fetus.

The abdominal cord insertion into the fetal abdomen, the genitourinary tract.

You wanna look at kidneys and bladder, the umbilical cord, the number of vessels and insertion into the fetal abdomen.

Again, people have varying opinions about where is the best place to look at the number of vessels in the umbilical cord.

Personally, I think it is very sufficient just to look at the cord insertion into the ventral abdominal wall and see two arteries coursing around the fetal urinary bladder.

This gives you a very easy assessment of a three vessel cord.

There are situations in which it can be three vessel at the ventral abdominal wall and two vessel elsewhere, but these are clearly the minority and the exceptions.

And I think if you're going to use this as sort of a standard exam, a screening exam, you should look at the fetal abdominal wall.

The cervical, thoracic, lumbar and sacral spine should be imaged and assess the extremities, legs, and arms, basically just to determine the presence or absence of them and the genitalia.

While this is often information sought on standard obstetrical sonograms is really only medically indicated in low risk pregnancies if there are multiple.

So if you're trying to confirm monozygosity, for example, you would want to show that both fetuses are of the same gender.

The lateral ventricle can be assessed quite nicely merely by identifying choroid plexus filling the lateral ventricle wall to wall the posterior fossa.

I like simply to look that determine that there is a cisterna magna.

This little bit of fluid has no, or higher brain function, but it nicely outlines the biconvex nature of the cerebellum it surrounds.

And finally, the cavum septi pellucidi is a reflection of four brain development without a corpus callosum forming.

Primarily, you will not develop a cavum septi pellucidi paucity.

The ventricle is mainly put in the guidelines to identify fetuses who have ventriculomegaly.

And again, this, there are wide variety of abnormalities that manifest as ventriculomegaly.

Obviously, you're gonna wanna look very carefully at the spine after you see ventriculomegaly and identify the gentle upturn of the sacrum and make sure there are no myelomeningoceles or whatnot.

If you don't see the skin covering or you see a sack in the distal spine, you may be able to identify a myelocele spina bifida.

But as you probably are aware, the most sensitive way to identify open spina bifida is to find that the cerebellum is compressed in the small posterior fossa giving it that C shaped or banana shape.

The cisterna magna is gone.

You no longer see that nice biconvex margin of the cerebellum.

This is a very predictive sign of a Chiari two malformation.

And if you see ventriculomegaly, I would strongly recommend you look carefully at the posterior fossa because open spina bifida is one of the most common causes, single most common causes of ventriculomegaly in the fetus.

Now we have become somewhat complacent with how great the posterior fossa is for identifying the Chiari malformation, which as you know, is almost always associated with open spina bifida.

And in fact, the spine may be more difficult to image than the posterior fossa.

So we've gotten pretty used to looking at the posterior fossa for finding myelomeningoceles.

And even if the posterior fossa is normal, I would strongly recommend you do not become too complacent about looking at the spine.

There are a number of abnormalities in the spine that can be seen with a normal posterior fossa that are unrelated to the Chiari malformation.

And this image is illustrating one of the most important ones.

In this case, you see that there is no gentle upturn of the sacrum.

Here's the iliac crest here.

The distal spine is almost completely missing.

This is a case of caudal regression and you will not detect this unless you make a point of imaging the distal spine in addition to the posterior fossa.

The upper lip is something you can find in well over 90% of mid gestation fetuses.

Once you get a little practice, it's very easy to see.

About 75% of clefts involve the lip.

The soft palate, as you know, has been a very challenging area for ultrasound, and we for all intents and purposes, miss most of the soft clefts.

But if you can find 75% by identifying the cleft in the lip, it would be very helpful both to parents and to enhance your search for additional abnormalities.

Four chambers included in the chest, very important part of the exam.

And when I say four chambers, I mean you need to count 1, 2, 3, 4.

There have to be four identifiable chambers on an axial view of the chest.

If you have an image like this, it's not gonna fly.

This in fact, was an example of left ventricular hypoplasia with fibroelastosis as you see here.

And I would strongly recommend if you can't get a four chamber image of the heart that you repeat the study.

Cardiac anomalies are the most common fetal congenital anomalies.

They're the ones that cause the most severe mortality and morbidity.

And really you should be able to get a four chamber view on every obstetrical sonogram.

So outflow tracks are recommended if technically feasible in the AIUM guidelines.

And I would like to emphasize this, I think we should make every attempt to get outflow tracks.

Once you're imagers get familiar with this imaging, it becomes very straightforward and very easy to do and can also be obtained quickly in an image very close to the one you use for your axial chest and your four chamber view.

And in this particular image, you can nicely see that.

You can see the RV outflow tract coming up here, crisscrossing with the LV outflow tract and the three vessel view just above that with the superior vena cava, the central aorta here and the pulmonary artery in that line.

Very important view.

This view will increase detection of cardiac defects on the obstetrical sonogram from a baseline of four chamber view of about 40 to 50% detection to 75 percent detection.

And I would strongly encourage your sonographers and yourself to become familiar with the outflow tracts and be able to obtain 'em in nearly every obstetrical sonogram.

The stomach, the presence or absence of it, the cord insertion into the fetal abdomen and the cord vessels.

You can see the cord insertion here.

This excludes basically omphaloceles and gastroschisis.

And the two arteries coursing around the bladder are pretty much all you need.

The stomach should be a single fluid filled structure.

You shouldn't see a filled duodenum.

If you see a filled duodenum, you must worry about some form of duodenal obstruction.

Obviously if you see a big mass of liver herniated out at the ventral abdominal wall insertion, you would be thinking of an omphalocele.

And if you only see one artery coursing around the bladder, that would be sufficient to make the diagnosis of a two vessel cord rather than a three vessel cord, which as you know, has a marginal increase in risk of anomalies, the renal region, including the urinary bladder.

You take a quick look at the kidney, sometimes you can't see 'em quite this well, but if you have a filled urinary bladder and normal amniotic fluid volume, then you're pretty much assured you have at least one intact kidney, one intact ureter, and a functioning urinary bladder.

If you see something like this, you would make the diagnosis of multicystic dysplastic kidney, but prognostically again, if it's a unilateral multicystic dysplastic kidney, it wouldn't have great prognostic implications as compared to a bilateral multicystic dysplastic kidney, which is basically like being anuric and is considered to be a lethal abnormality.

Conclusion

So the majority of cases that we do are standard obstetrical sonograms.

These should be the workhorse of obstetrical sonography.

The very minority of patients should be undergoing targeted obstetrical sonography.

I hope this has helped you and I think if you follow the AIUM guidelines, I feel very strongly they are very thoughtful guidelines.

They are very helpful, and they will keep you out of trouble and help you do a very good job.

Thank you very much.