AIUM Guidelines for Obstetrical Ultrasound - SD

Introduction

My name is Dolores Pretorius.

I am a professor at the University of California San Diego, and I'm going to talk today on the AIUM guidelines for obstetrical ultrasound from 2007, which are the basic guidelines we use.

Today I'd like to talk to you about the AIUM guidelines for obstetrical ultrasound.

The newest set of guidelines were adopted by the AIUM in 2007.

Previously, the American College of Radiology and the American College of Gynecology had adopted the same guidelines in 2003.

These are clinical standards that we can use as practice guidelines.

They are minimum criteria to complete the examination, which has been identified for physicians performing obstetrical ultrasound, and they're often used for a basis of a standard of care for malpractice cases.

Fetal Development Overview

If you look at the fetus and see how small it is on a scale, nine weeks and then moving up to 38 weeks, and all the way to term, you can see how the size of the fetus and the formation changes over time.

At seven weeks when the crown rump length is 12 millimeters, you can see that we barely have limb buds, a little ear bud, and that the head and neck are really quite large in comparison to the rest of the body.

But by 11 weeks when the crown rump length is 44 millimeters, you can easily see the arms and legs and face, eye, and ear.

Fetal Age Terminology

Now we talk about different ages for the fetus from conception.

We often call it conceptual age or fetal age, or gestational age.

And from the last menstrual period, menstrual age, ultrasound, we often call it ultrasound age.

And when we began doing ultrasound, we started talking about the gestational age based on the last menstrual period.

So there's a little bit of confusion in what each of these mean.

Now we also talk about what the fetus should be called from zero to 10 weeks.

It should be called an embryo.

And from 10 to 40 weeks a fetus.

We talk about cardiac activity prior to 24 weeks, and we talk about viability after 24 weeks.

That's because that's when we think the fetus could survive outside the womb.

AIUM Guidelines Introduction

Now, the introduction to the guidelines state that the fetal sonography should be performed only for valid medical reasons that we should use the lowest possible ultrasound exposure settings that the exam.

There will be limited exams in clinical emergencies or for limited purposes, like just to check for cardiac activity or fetal position or amniotic fluid index.

There can, we can do a limited exam for follow up after there's been a primary exam.

When we're looking to evaluate for growth or reevaluations of specific abnormalities.

The guidelines talk about a first trimester set, then a standard second and third trimester, and then the limited exam as we discussed earlier, specialized exams or cardiac echoes, detailed exams based on history or biochemistry like for alpha-fetoprotein or aneuploidy screening, and then specialized exams including the biophysical profile and doppler studies.

First Trimester Guidelines

Indications for First Trimester Scan

Now, the indications for first trimester scan are to confirm the presence of intrauterine pregnancy, suspected ectopic vaginal bleeding, pelvic pain, estimated gestational age, multiple gestations confirmed cardiac activity, chorionic villa sampling, embryo transfer, localization, or removal of IUD to assess for certain fetal anomalies.

This was added new in the 2007 guidelines that we finally now are recommending that fetuses be screened for anomalies, also pelvic masses in the mother or uterine abnormalities, and for possible high dad deform mole in the first trimester.

The exam can be done transabdominally, transvaginally or trans ally, whichever is appropriate for that clinical symptom.

First Trimester Exam Components

We are supposed to look for the gestational sac and we should evaluate the uterus, the cervix, and the adnexa for the location of that sack.

We should identify the presence or absence of the yolk sack.

We should identify where the embryo is identified and we should record the crown rump length measurement if we can see an embryo.

And if we cannot see the embryo, then we should measure the sack size for the presence or absence of cardiac activity, we should be able to see cardiac activity by the time the embryo measures five millimeters or greater.

If the embryo is less than five millimeters, then lack of cardiac activity tells us that we may need an additional exam to determine whether it's going to be a viable pregnancy in the long run.

Now here's a gestational sac and you can see the crown rump length.

Right here, the yolk sac to the right, this is the gestational sack, and here we have a measurement for the crown rump length in the embryo that measures 33 millimeters.

Multiple Pregnancies in First Trimester

The fetal number must be recorded in the amnity and chorionity should be documented for multiple pregnancies.

So what are we talking about?

We're talking about amnity and chorionity being whether they are diamniotic dichorionic like we can see in the upper and a here with two placenta in this case.

And four layers of membrane being a thick membrane.

The diamniotic dichorionic can also have a single placenta as seen in B and C.

We have monochorionic amnity and chorionity with a single placenta and a thin separating membrane there with the two Amnion.

And then in d, there's no separating membrane, which is monoamniotic monochorionic.

In this case, in the upper image, we can see a gestational sac with two yolk sacks and suggesting that it is have an amnion in between.

And in the lower right we have twins with very thick separating membrane that is consistent with diamniotic dichorionic placentation.

If we have multiple embryos, then we need to identify how many there are.

As you can see in this picture, we see 1, 2, 3, 4, 5 embryos in this single slice.

Diamniotic will once again have that thick membrane in the late first trimester, as you can see here with the placenta growing up in between them.

Whereas the diamniotic monochorionic will not have a twin peak and it'll be very thin and wispy here.

Going out to be identified as a dimo, we should see the gestational sac by five weeks.

The yolk sac by 5.5 weeks in an embryo by six weeks early work showed that if you had HCG levels by a thousand, we should be able to see a gestational sac.

By 7,200, we should see a yolk sac and by 10,800 heart tone, we remember this as the 1 7 11 rule.

Now a normal sac will have a nice decidual ring.

There may be a double decidual seen or may not, it'll be smooth.

The embryo, if we're doing transabdominal, should be present by 27 millimeters, whereas if transvaginal we should see it by five millimeters.

In general, we do do transvaginal in these early pregnancies to be able to identify them.

Here we can see a very small crown rump length with a little tiny yolk sac.

Abnormal Findings in First Trimester

Now an abnormal sac will have the sac size embryo and cardiac activity inappropriate for those gestational ages that we just recorded.

You may see angles in the sac or it may be collapsed.

There may be a poor decidual reaction, and if you do follow up studies, it'll grow less than 0.6 millimeters per day.

A pseudo gestational sac seen with ectopic pregnancies can also mimic a gestational sac.

So this is an abnormal gestational sac with a large yolk sac and really kind of irregular and angulated edges.

This also is an abnormal gestational sac with lots of multiple lucencies within it, and this would be something quite worrisome for trophoblastic disease.

Approximately 25% of pregnancies will have vaginal bleeding and approximately 50% will go on and spontaneously abort.

The guidelines tell us that we should look at the uterus, the adnexal structures, and the culdesac for presence, location and size of myomas and adnexal masses, and that we should look in the cul-de-sac for the presence or absence of fluid.

Here we can see a small fibroid sitting right behind this gestational sac at 10 weeks gestational age, and here we can see a molar pregnancy that is seen in this case with a viable fetus along with it.

But often our molar pregnancies will be seen in isolation as these multiple large irregular cystic spaces within the uterus.

Nuchal Translucency

In 2007, the guidelines recommended that we consider doing nuchal translucency measurements in order to assess risk for trisomy 21, 13 18, and anomalies such as cardiac defects, because fetuses with congenital heart disease often have an enlarged nuchal fold.

There are very strict criteria for doing this technique, and it requires certification in order to be able to take adequate images that can be used accurately for a screening.

Basically, if the measurement is greater than three millimeters, it is worrisome for a karyotype abnormality.

And in this diagram you can see that the fetus occupies about 75% of the image from the chest up to the head.

That we can see the amnion separate from the chorion and that when we measure it, we need to be very accurate on exactly where we put the cursors as this is the correct placement.

On the left hand image, we have a normal nuchal measurement of one millimeter.

In the middle image it's three, which would be borderline to abnormal, and we would need to correlate it with our blood test to be able to give a specific risk.

And then on the right you see the 10 millimeters, which is clearly abnormal and we'd be very worrisome for a karyotype abnormality.

Second and Third Trimester Guidelines

Indications for Second and Third Trimesters

Now I'd like to go on to the second and third trimester guidelines.

The indications for second and third trimesters is much longer than for the first.

You can see estimate gestational age fetal growth, vaginal bleeding, pelvic pain, incompetent cervix, fetal presentation, multiple gestations, adjunct to amniocentesis size, dates discrepancy, pelvic mass, suspected hydatidiform mole cervical cerclage placement, ectopic pregnancy fetal death, uterine abnormality, fetal wellbeing, amniotic fluid abnormalities, placental abruption, external cephalic version, premature rupture of membranes or preterm labor, abnormal biochemical markers.

Abnormal biochemical markers.

Follow up for fetal anomaly.

Follow up for placenta previa, history of previous congenital anomaly fetal condition in late registrants for prenatal care to assess for findings that may increase risk for aneuploidy.

That is a new one for the 2007 guidelines and screening for fetal anomalies, we need to look at fetal cardiac activity and notice whether the rate is abnormal and irregular or whether it's normal and that rhythm should be reported in the report.

Fetal Presentation and Multiple Pregnancies

We need to identify the fetal number again and the presentation.

The presentation will be cephalic in the upper first line of vox A in the second it'll be breech.

The third, it'll be a transverse lie with the head to the left.

And then the next one would be transverse lie, head to the right.

And you can see the variations of all these need to be dictated in your report.

Multiple pregnancies, just like the first trimester, we need to identify the amnity and chorionity because this makes a great impact on how frequently we could study.

These patients need to study them in order to find the complications of twins, and they do vary significantly based on the amnity and chorionity.

We need to do a comparison of fetal size and estimate the amount of amniotic fluid on each side of the membrane.

We generally do a single pocket.

The guidelines tell us we should at least say whether they're increased, decreased, or normal, and they do suggest that we should look at the genitalia and report it.

And that's because the genitalia will help us with the amnity and chorionity.

If they're different, what boy and a girl, it is likely that they came from two eggs.

Diamniotic dichorionic.

This is true most of the time, but occasionally patients with infertility do not read the books and they occasionally have and came from the same egg and still have different gender.

We also look at the placenta.

If there's a single placenta, we don't know, but if there are two placenta, we know that it's diamniotic dichorionic.

And then lastly, we look at the membrane.

When we evaluate that membrane, we need to determine whether it's thick, thin.

Some people will actually look at the number of layers, but the twin peak is very important in making this differentiation.

Now, Dr. Sbar talked at the, called it the lambda sign.

Other people call it the twin peak.

And it basically is when placenta is growing up between the two layers of the amnion.

Whereas in a monochorionic placentation, you can see that the placenta cannot grow up in between the two layers of the amnion because that chorion is holding it back.

Now, if you look at this picture of the placenta, it makes sense why you sometimes will see the peak and sometimes not, because if you have a section on the ultrasound coming through here, you might not see any twin peak.

Whereas if you went right through here, you would see a very nice twin peak.

So the point is that the placenta grows up in patches, it doesn't grow up along the entire membrane.

On the left, we see a twin peak and a diamniotic dichorionic placenta.

And on the right we see a very thin wispy membrane floating adjacent to the limbs of this fetus.

And we see no twin peak. This is a diamniotic monochorionic.

Twin triplets will have variations on the theme of amnity and chorionicity so that you can see a very thick membrane between B and C.

So that would be a di di.

And then on the there's either no membrane, which you can't see here, or there is a very thin wispy membrane going in between these twins.

And that would be important.

We need to compare the size between the two twins in order to assess them for intrauterine growth retardation between the two amniotic fluid.

We use the single deepest pocket in order to assess these methods.

Certainly if their pocket is less than two centimeters around a fetus that is worrisome.

Amniotic Fluid Assessment

In general, when we look at the amniotic fluid index in singletons, if it is between five and 20 centimeters, it's normal.

If it's less than five centimeters, we're quite concerned about being oligohydramnios.

And if it's greater than 20 centimeters and some people will actually use 25, then we are worried about polyhydramnios.

When you look at the four quadrants, you basically take a distance just drop down in order to measure those four quadrants.

And then a nice curve to the right we see of what is considered to be within normal limits.

And you see why the 20 to 25 it's not perfectly straight throughout gestation.

We take that measurement by dropping the line down, and we must have at least a centimeter of fluid pocket where we measure that in order to get the amniotic fluid calculation.

We take those four quadrants and we add them up to get the AFI, the placenta.

Placenta, Cervix, and Cord Evaluation

Cervix and cord also need to be evaluated.

We need to state where the placenta is and the appearance of it, it's relationship to the internal cervical os.

And also we note that the position early in pregnancy may not correlate very well with what will be late in pregnancy because as the uterus grows and enlarges during gestation, that placenta often moves up and out of the lower uterine segment as it stretches.

And what early on looks like a placenta previa later on will not be at all.

So anytime we see an early diagnosis of possible placenta previa, we wanna bring 'em back at about 28 weeks.

The guidelines also suggest that we should look at the number of vessels in the umbilical cord, and we should also assess for cervical shortening with transvaginal or a trans perineal scan.

So this is a low lying placenta that is approximately 1.8 centimeters from the cervix, which we can see over to our right here.

This is the urinary bladder, so we would call that a low lying placenta.

Now this is a 19 week scan and you can see that it looks like a placenta previa on transabdominal.

And when we go to transvaginal scanning and see the cervix, we can see the placenta is indeed covering the cervix and that would be placenta previa and we would recommend a follow up at 28 weeks.

Now we do look at the placental cord insertion into the umbilical cord insertion into the placenta, but this is not yet in the guidelines.

We feel this is important in looking for velamentous insertions.

The cervical length measures 4.9 centimeters in the case here, shown with the bladder anteriorly.

And in general, if your cervix is over five centimeters, it's just a little bit too long.

Now, if you have a question, you will need to go to transvaginal, as you can see here.

And this cervix measures 2.2 centimeters, and you can see the membranes bulging down into that cervix.

Gestational Age Assessment

Ultrasound should also be used for assessment of gestational age.

The crown rump length is the most accurate in the first trimester to assess for gestational age.

But as you go on to the second trimester, we use the biparietal diameter and head circumference that should be performed at the level of the thalami and the cavum septum pellucidum.

The cerebellar hemisphere should not be visible in the biparietal diameter, and we should measure from the outer edge of the proximal skull to the inner edge of the distal skull.

As you can see here in this diagram, the cavum is right up over here, and this is the midline falx and there's leading edge to leading edge now just recently in 2008, Peter Callen wrote a paper that was very helpful to us in noticing that the cavum has no echoes within it, whereas if you take it a little bit low, you are really in the forceps.

And then it is these forceps that tell us that we're a little bit too low in the fetal head in order to call it the accurate bi parietal diameter.

And why do we care?

Because we care because you can have agenesis of the corpus callosum with an absence of the cavum and that may be a very important sign for an abnormality of the brain.

When we look at gestational age, we not only do the BPD, but we also look at the head circumference and measure it at the same level as the BPD around the outer perimeter of the calvarium.

And here's another measurement showing the head circumference.

And you can see that this head is a little cephalic.

It kind of is boat shaped and looks a little bit flattened in the middle, and that is still a normal appearance to a head.

It is just going to have a more accurate head circumference than bi parietal diameter.

The femur length is the next structure we assess gestational age with, and it's pretty reliable after 14 weeks.

It's most accurate when measured with the beam of ultrasound being perpendicular to the shaft as shown in this picture.

And excluding the distal femoral epiphysis.

We also look at the abdominal circumference for assessment of gestational age.

Measuring at the skin line.

It's important to get a true transverse image at the level of the junction of the umbilical vein portal sinus and fetal stomach when present.

This abdominal circumference is used to estimate fetal weight and it may allow detection of IUGR and macrosomia, and this is the level we like to take it with the stomach and the hockey stick or the umbilical vein coming in.

It's very important to look and see where these calipers are put, particularly in the third trimester as it's really easy to underestimate the size of the abdomen if you're not careful.

Now, in general, we use a variability of dating rule that in the teens it's within one week of variability.

In the twenties it's within two weeks, and in the thirties it's within three weeks.

But there's a caveat to this that if you have a prior ultrasound, then you should be growing within about a week of your original ultrasound dates.

Intrauterine Growth Restriction

Intrauterine growth restriction, the causes are congenital anomalies, infection, maternal nutrition, maternal hypertension, maternal smoking and drugs, just to name a few.

In general, how do we make this diagnosis?

We do serial ultrasound studies.

We find a small bi parietal diameter or a small abdominal circumference.

We look at the head to abdomen ratio, and if that's not correct on the tables, then that's worrisome.

We look for oligohydramnios and abnormal doppler studies.

There's two types of intrauterine growth restriction.

Number one is symmetrical where both the head and the body are delayed, which tends to be more frequently in the second trimester, whereas asymmetrical intrauterine growth restriction is caused in the third trimester and it has head sparing with the body being smaller in the head, being more normal.

In general, the symmetrical types are much less common, only 25% and the asymmetrical ones are more common.

How do we estimate the fetal weight?

We use those parameters, the bi parietal diameter, the head circumference, the abdominal circumference, and the femur length.

We look at interval measurement changes, and these can be performed every two to four weeks, depending upon what time in gestation it is.

We usually do them more further apart when we're in the second trimester and closer together in the third trimester.

The error may be as high as 15% in estimating the fetal weight.

And at our institution at the University of California San Diego, we take three measurements of the abdomen circumference in the third trimester if it's an abnormal number or if the patient is diabetic.

We do look at the growth curves in order to assess for fetal growth in the third trimester, and these would be fairly normal measurement up on the left.

But you look at the abdominal circumference, it's going up above the 95th percentile in the curve on the right.

Maternal Anatomy

Okay, we also need to look at the maternal anatomy to look at the uterus, the adnexa, and once again, the presence, location, and size of myomas and adnexal masses.

So this is a left ovary that we can see is a normal structure, whereas this is a fibroid that is living in the retro placental region in the upper left hand corner in a pregnancy at 19 weeks.

We can see this fibroid over here under the placenta as well.

When they're retro placental, they have an increased incidence of abruption when it gets closer to delivery and intrauterine growth restriction.

This is kind of interesting fibroid, kind of sitting right inside the amniotic fluid.

Fetal Anatomic Survey

Now the fetus also has to be looked at for an anatomic survey, and this can usually be done after 18 weeks gestational age.

There will be technical limitations in some patients that are larger or when the fetus is in an unusual presentation and follow up may be helpful in those cases.

So we're gonna go through the fetus from head to foot.

Head and Neck

When we look at the fetal head and neck, the guidelines tell us we need to look at the cerebellum, the choroid plexus, the cisterna magna, the lateral cerebral ventricles, the midline falx, the cavum septum pellucidum, the upper lip, and the nuchal fold, both of which were added in the 2007 guidelines.

So we look over at this picture of the head and you can see the cavum septum pellucidum.

We can see the cisterna magna with the posterior fossa.

And you can see the nuchal fold sitting right back here.

You measure from the edge of the cranium to the edge of the skin there, and you do need to be at the level of the cavum, the choroid.

You need to measure the ventricles from the medial wall to the lateral wall where you see two bright echogenic lines.

Once again, the cavum septum pellucidum with no central echo within it.

The palate is not yet in the guidelines, but it is something we do at the University of California on everyone.

And these, this is the palate with the primary palate here in the secondary palate posteriorly and in the back.

The lips, as we said earlier, have been added to the guideline.

This is the upper lip.

And you can see the two nostrils right here of the nose.

This would be the lower lip.

The nasal bone is not yet in the guidelines, but it is something that is becoming more commonly done.

And we do it on all of our patients in our lab.

For the risk of aneuploidy and down syndrome specifically, you can see that this is the chin of this fetus.

Chest and Heart

After the face we go look into the chest where we look for the four chamber view of the heart and we attempt to evaluate both outflow tracks.

The four chamber of the heart is here.

You can see these diagrams showing the normal axis of the heart of 45 degrees axis when you look at the spine towards the sternum.

And you can see the two atria, the two ventricles similar in size.

The heart occupies about a third the size of the chest.

We look for an intact septum and an intact crux as well as the position of the valves themselves.

So we should try to get one rib on each side to get a normal four chamber.

Not always easy to do.

You can see here we have a normal four chamber and we only have one good rib, so it's not always necessary.

It just can be helpful. There is the crux.

You can see that the tricuspid valve is just a tiny bit lower than the mitral valve, which is important.

The left outflow tract comes from the left ventricle, that's from the aorta, sweeping along here, and that's very important to look for VSDs as well as malalignment because if the aorta goes over into both ventricles, then we worry about transposition of the great vessels.

Truncus or tetralogy, double outlet right ventricle.

This is a picture of the right ventricular outflow tract.

We call this the sausage and the egg view.

We like that radiologists love food.

Here is the sausage and here is the egg and that's the aorta in the middle with the pulmonary artery here with the pulmonic valve coming right out of the right ventricle.

And you can see the right atrium here with that tricuspid valve.

Just like in the diagram to the left, we move on to the abdomen.

Abdomen

We look for the presence size and situs of the stomach, meaning whether it's on the left or the right.

We look at the kidneys, the bladder, the umbilical cord insertion site into the fetal abdomen and the umbilical cord vessel number.

So here we have the stomach on the left and the spine is over here.

And you have to know the position of the baby that this is in its cephalic position with the spine to the left and the left side down.

These are the kidneys.

And in order to identify the kidneys, we need to see a little bit of psoas fascia here, or a little bit of the pelvis.

And there's a little bit of the pelvis in order to say that we are certain that there are kidneys there.

And there's a nice bladder, fluid filled collection in the pelvis.

At 10 weeks we can see some bowel that fit herniates out into the cord.

This is normal physiologic herniation.

It should be back into the fetal abdomen by the end of the 11th week.

So here you can see in the same fetus at 12 weeks.

It's back inside the abdomen, so that is normal a normal cord insertion.

Later on in the second trimester, we should see fluid on both sides of the umbilical cord.

When we go down to look at the vessels in the cord, we usually take this picture, which is a color picture, using power doppler showing the two hypogastric arteries alongside the bladder as they enter into the fetus.

And that tells us that there is a three vessel cord with two arteries.

Now the iliac arteries are similar to the hypogastric arteries, and so it is important to make sure that you know where the vessels are coming in.

These would be the iliacs, whereas these would be our umbilical arteries coming in.

Now the umbilical cord can also be identified within the amniotic fluid, and you can see those two arteries in two veins.

In both of those pictures, we talk about them as the mickey mouse ears.

Spine and Extremities

We need to also look at the spine, looking at the cervical, thoracic, lumbar and sacral spine, and the extremities, the legs, and the arms.

Now when we look at the spine, we need to not only look in longitudinal, where you see the picture in the upper left where it looks like a zipper, and you can see all of those vertebral bodies paired.

As you look at these are paired as you go along so that if they're abnormal, you would see it.

The thoracic spine, we need to look at the entire spine and transverse it all where we count 1, 2, 3 coming down, 1, 2, 3, and then to the sacrum once again.

And we also look at the skin on top to make sure we don't have any spinal defects.

The upper extremity, we're supposed to look at those extremities.

So we take a picture showing the humerus and the radius and ulna with the hand below.

And we don't take open hands on everyone, but we do try to, in some patients who are at increased risk, the lower extremity, we take pictures of the lower leg and of the ankle.

We need to take pictures of the gender in multiple gestations, but in singletons.

It's not necessary in the low risk pregnancies, but most of our families in our culture would like to know the gender and they feel much better if you can tell it to them.

So I'd say about 80% of patients want to know their gender, and it'll all depend upon your patient population.

This is a male with the two legs spread and you can see the scrotum and the penis right in the middle.

Permanent Records and Equipment

Now the guidelines also tell us that we need to record a permanent record of our images, and we need to record the measurements so that when we take that picture that comes up on the computer, we need to actually print it out some way.

It's also important to label the images with the exam date, the patient ID number, and if appropriate, the image orientation, for example, whether it's sagittal or transverse, and also whether it's right or left sided.

Since the fetus moves around, you don't really know if it's an abnormal right kidney.

We'd like to know that and that there needs to be a written report, the equipment that we're supposed to use, they, the guidelines tell us that we can use realtime scanners, transabdominal or transvaginal, that the transducer should be using the appropriate frequency for whatever you're trying to look at.

That realtime sonography is necessary to confirm fetal life through observations of fetal cardiac activity and active movement.

Fetal Safety

Now for fetal safety, ultrasound is considered to be safe, but we should only perform it when there's a valid medical indication, and that's because we wanna use the lowest possible ultrasound exposure settings when we can to use the same principle, the ALARA principle that we use for radiation, which is as low as reasonably achievable.

Now, ultrasound does have bio effects and there are, the bio effects are predominantly related to thermal effects and mechanical effects.

The energy levels depend on the machine settings that you're used.

The MI, which is the mechanical index, and the TI, which is the thermal index, are both listed on our images.

Now, some images will only have the mechanical index on them, and some of them will only have the thermal index on them.

But both of these, we wanna try to keep below one, 0.0 if we can.

Now, when we turn on color, we will always increase those indices a little bit, particularly the thermal index.

And we want to use color very briefly when we turn it on.

Now, the bio effect studies that have been done with ultrasound are all done based on old limits of 94 milliwatts per centimeter squared.

But as the technology has developed, we now have much higher limits, and we use 720 milliwatts per centimeter squared.

But all of the bio effects studies have not been repeated because basically in our culture, greater than 80% of women get ultrasound exams.

And we can't really do those same studies that were done early on.

So the main point for you is that you don't sit and scan a fetus forever.

You mainly try to get in, look at what you need to look at and then get out, because raising the temperature in the fluid around the baby is not healthy for it, and we don't wanna do it for prolonged periods of time.

The AIUM tells us that the promotion, selling or leasing of ultrasound equipment for making keepsake fetal videos is considered by the FDA to be an unapproved use of medical device in the United States.

Use of a diagnostic ultrasound system for these purposes without a physician's order may be in violation of state law or regulations.

Policies and procedures related to quality, patient education, infection control, safety, and equipment performance monitoring are all a part of those guidelines, and they must be developed and implemented according to the AIUM guidelines.

So there are additional guidelines telling us how to sterilize our transvaginal probe, for example, and about safety beyond what we've gone over today.

Conclusion

That's the end. And thank you very much.