Early Anatomic Evaluation - SD

Introduction

Hi, I am Dr. Phyllis Glance, an associate professor at the University of Toronto.

I'm cross appointed in the Department of Obstetrics and Gynecology, but my primary appointment is in diagnostic imaging.

Most of my career has been spent in the area of perinatal imaging, obstetrics and gynecology.

And today I'm pleased to share with you some of my thoughts about early anatomic evaluation.

Learning Objectives

Hello everyone. We're going to spend the next half hour or so talking about the early anatomic evaluation and our learning objectives for this session are to consider what are the drivers of early anatomic evaluation, the role of NT screening, the role of dedicated anatomic evaluations, and looking at some future directions.

Shift in Anatomic Evaluation Practices

In many ways, I've begun to think about anatomic evaluation as an any time process.

In the old days routine, fetal anatomic scan took place at 18 to 22 weeks and was essentially a transabdominal sonogram.

We began to see a shift towards the 11 to 14 week nucle translucency or NT screen done transabdominally.

With that, of course, people began to feel, well, maybe we should be adding in anatomy either transabdominally or transvaginally, and then well maybe the baby will be just a little bit bigger and we can do a combination of transabdominal and transvaginal sonography at the 14 to 16 week period.

So there's been a tremendous shift in our thinking about when to do anatomic evaluation.

And for the purposes of this session, we're going to concentrate on the 11 to 14 week time period.

Drivers of the Shift to First Trimester

Why have we seen this rapid shift into first trimester?

We're seeing patients earlier predominantly because of screening programs.

There are many guidelines out there that require us to offer a combined maternal serum screen and or NT evaluation program.

Transvaginal ultrasound has improved technology has a very high acceptance and familiarity to both the patient and the physician.

We have a broader understanding of embryology and a recognition that most congenital malformations have formed by the end of the embryological period.

We would all like to avoid the possibility of a late termination.

So if one continues to perform the routine timing at 18 to 22 weeks, there are potential delays which may occur while one waits for karyotype analysis, a repeat evaluation, perhaps an MR or an echocardiogram, perhaps torch titers.

And during that time period we may end up in to where a point in time where the fetus is now viable.

So there's both tremendous physical and psychological morbidity that can be associated with a possible late termination.

Effects of Early Anatomic Scan

What are the effects of the early anatomic scan?

Well, at the end of the day, there is an increased cost to the healthcare system.

We still do recommend a follow up 18 to 22 week anatomical evaluation and it does instigate additional interim examinations.

It requires a different expertise.

We have the MFM UK driven N NT certification program.

There is a learning curve, to both performing early anatomy transabdominally as well as transvaginally.

There's new knowledge we need to obtain including that of embryological development.

And as Ty all demonstrated transvaginal anatomy itself can be somewhat more challenging than many of us had anticipated.

There are safety concerns with exposing the fetus at an earlier stage to ultrasound output.

In particular when we perform pulse spectral doppler analysis.

And of course we're bypassing the natural selection process by coming in at an earlier time point.

Who Should Receive First Trimester Anatomy

So to who should we offer first trimester anatomy?

And perhaps the answer is we should offer it to those at most risk in the current pregnancy.

Those patients who present with an increased NT value or maternal indications such as known, inherited or recurrent conditions, maternal exposures or diseases with fetal risk, or patients who are prone to incomplete anatomy at 19 to 21 weeks.

Benefits of Early Anatomic Exam

What are the upside or positive potential of the early anatomic exam?

The bottom line is that it does permit us to come in earlier and identify fetuses who are aneuploid or have congenital anomalies.

And again, in turn this permits the option for earlier termination or for CVS sampling.

It does provide reassurance in the at-risk population with a normal study.

It does triage a group for potential transfer of care to a tertiary facility in those that wish to continue the pregnancy and it helps establish ity.

There's also we believe a role for first trimester anatomy in the obese woman, obesity is defined as A BMI or body mass index greater than or equal to 30.

About one third of women in the reproductive age group in the United States will fall into this category.

These women are at increased risk for congenital anomalies.

But unfortunately due to suboptimal imaging through the abdominal wall panis, there is a decreas detection rate of those congenital anomalies and an increased number of incomplete and suboptimal studies.

So there is speculation that coming in transvaginal at an earlier point in time when the fetus is within the range of the transvaginal probe may be a benefit to this particular patient group.

This is not yet evidence-based and we continue to wait for definitive studies on this area.

Optimal Timing

What is the optimal timing?

It's well recognized that completion rates increase with gestational age in the average weight person up until about 15 weeks.

A detailed evaluation is possible in the majority of patients by 13 weeks.

If we think about first trimester anatomy and the 11th to 14 week NT examination, it's important to recognize that these are not equivalent studies.

The 11th to 14 week NT evaluation is really a risk estimate for fetal aneuploidy.

It is not a diagnostic or morphological evaluation.

NT Screening

There are many different methods of screening in first trimester and this is a classic chart from ides group demonstrating the performance of different methods of screening for Trisomy 21.

And if we just add NT to menstrual age, we should be able to achieve a detection rate of 75 to 80% at a false positive rate of 5%.

If we add in blood serum chemistry, we up our detection rate by approximately 10% while maintaining a 5% false positive rate.

And this is where many screening programs have gone towards, although we call it the 11 to 14 week NT evaluation.

In fact, we perform it when the crown rump length is at 45 to 84 millimeters.

And its primary purpose as we've mentioned, is to determine the fetal aneuploidy risk based on a combination of NT maternal serum screen and menstrual age.

We also use it for dating to provide an accurate CRL for serum biochemistry to identify a failed pregnancy to establish genicity.

And lastly, to evaluate or define anatomic abnormalities.

Most of us are quite familiar with the technique.

We like to have the fetus in a sagittal neutral midline position.

We zoom so that the face and upper thorax occupies virtually the entire screen and we take the largest measurement and we do wanna make sure that it is well away from the amnion.

And this is the classic caliper alignment for NT measurement diagram put out by the MFM UK Foundation that demonstrates the caliper of the crosshatch of the caliper should be inner to inner.

Increased NT and Associated Conditions

So what does it mean to have an increased nt as we see on the patient on our bottom visually a normal NT is smaller than that of an increased NT on your right.

If there's a normal karyotype, the majority of these will have a normal outcome.

The larger the nt, the worse the prognosis.

And even in the setting of euploid, we will recommend a fetal echocardiogram to be performed.

So increased NT is quite common in a number of conditions.

TRI 21 where we also look for additional findings such as absent nasal bone or an A VSD trisomy 18, also associated with phae congenital heart disease, musculoskeletal abnormalities and intrauterine growth retardation Trisomy 13, we look for common associated findings such as holo proin, Kali congenital heart disease, and on foil turner syndrome or XO congenital heart defects.

There's a 24 times increased risk in the setting of an increased NT and various syndromes such as musculoskeletal dysplasias.

Cystic Hygroma and Hydrops Fetalis

Just going to step aside from NT for a moment and discuss cystic hydroma and hydrops fatalis cystic hydroma is sort of an NT on steroids, so it extends way beyond the NT region as we see in this case.

And it's often complex with multiple septations present and extends down along the body.

Half of these patients will have aneuploidy with tri semi 21 being the commonest cystic hydros occur in virtually 90% of Turner syndrome or exo syndrome.

In the half that are euploid, at least half of these patients will have a major structural fetal malformation of which cardiac will be the commonest.

Again, the reason in the euploid population to recommend a fetal echocardiogram hydrops fatali on the other hand is a cystic hydroma in combination with ascites effusions, a wave reversal in the ductus osis or tricuspid regurgitation.

So generalized subcutaneous thickening plus some additional signs.

Natural Attrition of Aneuploidies

The question always comes up, if we didn't do first trimester screening at the 11 to 14 week, what would happen?

What is the natural attrition of the commonest of these aneuploidies after 12 weeks to term?

And in fact, there is a natural attrition or intrauterine fetal demise and trisomy 21 of about 30% in trisomy 18 and trisomy 13 approximately 80%.

And we compare this to the euploid population where it's down about one to 2%.

So the risk of aneuploidy, from 12 weeks to term in a 20-year-old, we can appreciate for example in trisomy 21 the incidents will drop from one in a thousand to one in 1500.

Whereas in a 30 5-year-old the incidents will drop from one in two 50 to one in three 50.

And similarly for the other two aneuploidies here, the exception is turner's where the risk of fetal death remains the same despite the age of mom.

So women over 35 years of age, which only represent 20% of the pregnant population carry a burden of about 50% of all trium E 21.

Beyond NT Screening

Once we are finished with the NT evaluation, what goes beyond this?

We have more acronyms that have come down the road at us in particular NB and it NB refers to nasal bone.

And what we look for in this setting are two parallel lines or an equal sign between the tip of the nose and the frontal bone.

And so here at the nasal tip we have an echogenic line at the interface of the skin and the frontal bone.

There's an echogenic line and then just parallel and beneath that is the nasal bone.

And we contrast that to the picture on your right where there is no nasal bone under underlying the echogenic line of the skin interface with the amniotic fluid, the nasal bone in first trimester acts as an independent variable.

The presence of a nasal bone will reduce the aneuploidy risk about three times and absent nasal bone increases the risk.

But we caution to wait till after achieving a CRL of approximately 65 millimeters or 12 weeks gestational age.

An absent nasal bone will occur in 67 to 73% of Trisomy 21 giving a likelihood ratio of about 48 times an absent nasal bone will also occur in 1.5% of the euploid population.

When we break this down by ethnicity, the incidences in the OID population is only half a percent in Caucasian but increases to 8.8% in Afro-Caribbean, giving a likelihood ratio of 7.4 and up as high as 12.5% in the oriental population.

So the absent nasal bone has to be looked at on the basis of ethnic variation.

There's been a lot of literature looking at nasal bone lengths.

At the end of the day I think it's a somewhat less reliable parameter than present or absent, but there are number available that we can use in the interim and probably the best single number to remember is that the nasal bone length should achieve at least 2.5 millimeters by the end of first trimester.

What about in second trimester?

The absent nasal bone at 15 to 20 weeks just gestational age will increase the risk of trisomy 21 by 83 times a hypoplastic nasal bone has a significant indicator for trisomy 21 as well giving a detection rate about 60% with a false positive rate of 1%.

And this would be similar to the detection rate of by using menstrual age and maternal serum screen alone and has been published widely.

There are many additional findings to look at for the detection of Trisomy 21 in second trimester.

One of the issues that have not yet been addressed is that there are actually two nasal bones, one just on either side of the absolute true midline.

So a unilateral absence or presence of the nasal bone has not yet been fully addressed in the literature.

And something to caution and look out for here we have a series of three images demonstrating the nasal bone appearance in second trimester.

The image on your left is a normal fetus euploid at 20 weeks and the arrow points to the equal sign and the nasal bone underneath the middle image is a fetus affected by trisomy 21 at 20 weeks gestation and the arrow is pointing to a markedly hypoplastic nasal bone.

The image on your right is again an infant affected with trisomy 21 at 22 weeks gestational age and there is an absent nasal bone.

So it's believed that an absent nasal bone and hypoplastic are likely the single most effective marker.

Now for trisomy 21 in second trimester, it is one of our new acronyms for 2011 and it stands for intracranial translucency or the fourth ventricle.

And we see this small intracranial translucency surrounded by the brainstem in front and the choroid plexus in back.

And if we look a little closer, it's really very parallel in its appearance to the al translucency.

Why do we wanna look for an IT with the nt?

We recognize the NT at 11 to 14 weeks is the single most effective sonographic marker for T 21 and major aneuploidies when it's combined with menstrual age, maternal serum screen, NT and nasal bone, we're actually able to identify as much as 95% of major aneuploidies for a false positive rate of 3%.

But what we haven't caught is spina bifida.

And this remains a challenging diagnosis in the normal fetus.

The IT or intracranial translucency here is always visible measuring somewhere between one and a half to two and a half millimeters at 11 to 13 weeks.

It's parallel to the NT on a slightly para sagittal plane to the midline.

And the concept here is that most open spina bifida is associated with the Arnold Keri malformation and it's hypothesized that the Arnold Keri malformation occurs secondary to a leakage of CSF into the amniotic cavity resulting in hypotension in the subarachnoid space, subsequent codal displacement of the brainstem and obliteration of the cisterna magna and fourth ventricle with loss of the IT appearance.

And if we look at a case demonstrating this, these are images again from Nicolaides group.

We see a normal fetus on your left and on the right there's been a prolapse of the brainstem into the upper C spine in this infant affected by Arnold Chiari malformation and a loss of that IT space.

Anatomic Evaluation at 11 to 14 Weeks

We're going to switch gears a little bit now and think again about the 11 to 14 week NT evaluation but look beyond it at anatomic evaluation.

And from coming out from the ides group again, they suggested that perhaps there are three major diagnostic categories that we can think about.

There's a group of abnormalities that we should always detect at 11 to 14 weeks and this would include an Kali, a lower holo Proin, Kali body al anomaly on fall, gastro ISIS and mega cysts.

There is a group which we can potentially detect and these include a variety of entities such as cardiac disease, skeletal dysplasias, lymph amputations, open neural tube defects, renal agenesis, facial clefts and diaphragmatic hernias.

And then there's a group which generally we will not detect at 11 to 14 weeks in part related to developmental time or to time of acquisition of the disease.

For example, agenesis of the corpus close.

And we would not detect as it's not fully developed at that time, fetal tumors may develop later, hydronephrosis may develop later and so on.

So we're going to focus for the purposes again of this session on the always detect group and we'll begin with Annin Kali and holo proin Kali.

Anencephaly

So our first one is Annin Kali, but we're going to look at it as the Xin Kali Annin Kali sequence.

Xin Kali is defined by the absence of the calvarium in association with a mass of dys genetic or dysmorphic brain tissue.

And if we look at this case at 11.3 weeks gestational age, there's a dysmorphic mass of brain tissue sitting above the spine.

The orbits are here.

There are no normal midline structures or corpus callosum.

This is a 12 week image and no vault ossification.

And we expect to see frontal and parietal ossification having started by 10 11 weeks.

And it's believed that over time this exposed brain will degenerate due to the injurious amniotic fluid environment and repetitive trauma eventually evolving into the classic appearance of annin Kali Annin.

Kali remains the commonest neural tube defect occurring in one in a thousand bursts with a recurrence risk of about 1.9%.

In most cases maternal serum alpha-fetoprotein is elevated and folic acid administration is preventative in about 70% of cases.

So we believe that we're seeing a sequence in time and if we look at this video clip a little closer, you may again appreciate the large mass a brain tissue existing supraorbital disorganized with no normal formation.

So again, embryology and the time in which we expect to see normal structural intracranial development and that knowledge is very important.

And this mom in fact had had a previous pregnancy diagnosed as an encapsule, was put on high dose folate for the current pregnancy and unfortunately, still recurred in review of the previous case.

We believe that the first, that the previous infant had been affected with X in CLI as well a lobar hole.

Holoprosencephaly

And pro Keli is the second of the intracranial diagnoses that we should always be able to perform.

And again, much of this information has come from the IDE group.

The prevalence of this disease is about one in 1300.

Two thirds of these are aneuploidy, typically trisomy 18 and 13 and one third are euploid.

You might ask the question why karyotyping a clearly fatal prognosis and that's about counseling for recurrence.

There's approximately 10% recurrence risk if aneuploidy is present and a 1% recurrence risk if euploidy is present.

And in the euploid situation, we want to check for associated genetic conditions again to be able to counsel more effectively for subsequent pregnancies.

A LOBO hole in pro Kali has a very classic appearance and I remind you of the 12 week appearance of the cranium bone ossification has begun in the frontal and parietal bones.

A midline false is present and the choroid plexus are seen filling the lateral ventricles.

Clearly this 12 week image is abnormal and what we see here is a lack of midline structures.

There is a single mono ventricle and fused thalami and this theme is reiterated in these additional cases in these three different cases of holo proin carefully, we sometimes can appreciate the displaced pancake of compressed cortical tissue.

Sometimes a little more posterior in some cases, but in all cases clearly abnormal.

We should be able to make this diagnosis after 10 weeks gestation because of the lack of normal midline structures.

And as in many of these situations, spontaneous intrauterine fetal demise is relatively common.

There are some common facial features and I draw your attention on this sagittal image to this soft tissue protrusion, which is present supraorbital and can be seen as a little nodule just in front of the forehead.

If we go a little lower down on those images, you appreciate two born bony orbits very close together, almost united.

So classic facial features, a SCUs or soft tissue protrusion supraorbital in setting with of extreme hypos or even cyclo OPIA 3D ultrasound can be helpful at times.

The arrows in these two different cases are pointing to a SCUs and the case on your right where we're looking face on at the fetus.

You may appreciate that the two bony orbits are very close together consistent with extreme hypothyroidism.

Gastrointestinal Malformations: Abdominal Wall Defects

We're going to switch and look at some of the gastrointestinal malformations that we can identify.

I like to classify fetal abdominal wall defects by using the umbilicus as a reference point.

And for the purposes of this talk we're going to concentrate on the two we should always detect on falle and gastric isis.

For on falle, the important issue is to distinguish it from the normal midgut physiological herniation of small bowel.

Both of these entities insert into the base of the umbilical cord and it's quite normal to see this midgut physiological herniation, but there are some parameters.

It should measure less than seven millimeters at any age.

It should be less than 10 millimeters at 10 weeks of age and should be gone by 12 weeks and it should never contain liver.

And on falle on the other hand, may measure more than seven millimeters under 10 weeks, more than 10 millimeters after 10 weeks and may persist beyond 12 weeks.

And when liver has been extruded it tends to be more homogeneous and rounder in appearance.

And the picture we have here on the bottom is that of a giant on fall seal 16 by 20 millimeters containing liver.

Two additional images of phae at 12 weeks gestation.

On your left is a euploid fetus with the upper arrow pointing to the liver and the lower arrow pointing to some small bowel which is herniated into the base of the umbilical cord on your right is an image of a fetus at 12 weeks with an phae containing liver.

A very rounded appearance and this particular infant was affected with trisomy 18.

In general, if only small bowel has herniated out, the association with tri semi 18 is higher than if it's a combination of small bowel and liver or liver only.

Unfortunately, 70 to 90% of fetuses with an AL seal will have associated anomalies.

The most common being cardiac.

Only 17% will survive till surgery due to a combination of termination of pregnancy, intrauterine fetal demise or early neonatal death.

And the majority of these as you might imagine, are associated with increased alpha fetal protein due to the membrane surrounding them.

Gastric isis is quite different in that it's not a herniation into the base of the umbilical cord but is actually an abdominal wall defect.

Typically as we see in this case to the right hand side of the umbilical cord, it is not surrounded by membrane.

So we have herniation of free floating loops of bowel.

Clinically there's an increased incidence in patients under the age of 25 and those who are substance abusers in particular cocaine, the aneuploidy risk is almost zero so that we don't routinely recommend karyotyping and only 5% have associated structural anomalies.

Nonetheless, these require very close surveillance, particularly in third trimester.

About half of these fetuses will be affected by intrauterine growth retardation and oligo hydrus.

Spontaneous intrauterine fetal demise is a risk.

They may develop a protein losing enteropathy or bowel obstruction and polyhydramnios.

There has been no good correlation to the degree of bowel wall thickening or dilatation that occurs 80 to 90% will survive if the gastric ISIS is an isolated abnormality.

However, the actual outcome will depend on associated bowel abnormalities.

One third of these infants will be quite disabled, suffering from gut atresia, short gut syndrome or hypo motility syndromes.

Genitourinary Malformations: Megacystis

Our last section that we're going to look at is genital urinary.

And in our must diagnose category is mesti in first trimester.

Normally we should visualize urine in the bladder by nine to 10 weeks of age.

We can identify the bladder by its location between the two umbilical arteries and over seven millimeter in vertical diameter.

About a third of patients will have aneuploidy again, typically trisomy 13 or 18 when the bladder measures over 15 millimeters in vertical dimension, virtually all will experience a progressive obstructive pathy in the 17 to 15 millimeter range.

90% will resolve if OID and it's believed that there's a transient functional neurogenic bladder with a delay in smooth muscle autonomic innervation.

So this group we can consider re-scanning in two weeks and perhaps performing karyotype analysis in this particular fetus.

The vertical dimension of the bladder was 12 millimeters and indeed it was a transient mesti which resolved spontaneously the case on your right, the vertical dimension of the bladder is 17 millimeters and we've mentioned that once past 16.

The majority of these will continue on to a progressive obstructive neuropathy.

And if we look at this case a little bit more closely, the yellow arrows are pointing to potential early renal collecting system dilatation and the last arrow pointing to a keyhole appearance of the inferior aspect of the bladder or possibility of a distended posterior urethra.

And indeed the diagnosis in this case was posterior urethral valves.

So, this one will do well.

This one almost certainly will have a dismal prognosis.

So what about posterior urethral valves in the setting of euploid?

If the bladder is significantly distended, the majority will go on to an obstructive uropathy.

But the key to good prognosis will be based on fetal urine electrolytes.

And we like to see a sodium under a hundred milli equivalents per liter.

A chloride less than 90 milli equivalents per liter and an osmolality less than 210 no ultrasound evidence of renal dysplasia.

And the survival rates are about 81% in those with good fetal urine electrolytes versus 12.5% in with poor urine electrolytes.

In terms of prognosis, shunting is not often recommended any longer.

Those fetuses who have undergone shunting and have poor urinary electrolytes mortality remains fairly high with dismal long-term outcomes.

The keyhole sign or dilatation of the posterior urethra as we see in this case was thought for a long time to be fairly specific for posterior urethral valves.

However, I would we submit that it is highly sensitive but no longer should be considered specific for posterior urethral valves.

It does remain your first thought in a male fetus, whereas in a female fetus we would consider urethral atresia.

What is quite interesting is that some studies have demonstrated that as many as a third of boys with vesical ureter reflux may demonstrate a transient keyhole sign, likely on the basis of bladder dys syner.

So what's important here is to determine whether this keyhole sign is permanently there or transiently there.

And if it's transient, consider vesical ureter reflux.

Future Directions

Well, we're gonna take a little bit of a look at some future directions in ultrasound and of course, we can never resist a lovely image of a moving baby.

And here we see what some of the new matrix probes are able to give us with representation of gray scale and four D imaging simultaneously.

And we expect again to see further developments along this field.

For some of you who are really looking at the images, you may notice that this is a twin pregnancy and there is another baby just below the one that we're seeing actively moving.

Comparison with Second Trimester Evaluation

So at the end of all this discussion, how does first trimester evaluation anatomy compare with second trimester?

The largest prospective trial was performed by salted etal and at the end of the day their conclusion was there was no detection rate advantage, but it permitted termination earlier and that most lethal malformations were detected less than 15 weeks gestational age.

And this is a study that was published in 2006 and certainly the more recent literature that we've been looking at in terms of the always detect group is very consistent with this information.

Whether in the usually detect or may detect group between 2006 and 2011, we'll now begin to see a higher detection rate remains unknown.

One of the interesting areas, to keep an eye out is that of doing fetal echocardiography at the 11 to 13 or 13 to 15 week time.

We recognize that congenital cardiac disease is the commonest abnormality and yet one of the worst for us to detect in routine timing.

Hopefully there's some potential to improve our detection rates by doing early anatomy evaluations.

Gel al looking at 6,000, fetal echocardiograms at 13 to 16 weeks was able to demonstrate a complete visualization of cardiac anatomy.

When the lie was favorable published in March of 2011, the Ides Group demonstrated that they could identify 95% of cardiac defects with 84% correct diagnosis.

So these are very startling numbers and we need to determine if perhaps this is a better time to come in or we can be better at what we do.

And certainly, these, cases of first trimester diagnosis.

Your top one is at 13 weeks a hypoplastic left heart syndrome where, the two images on your left are pointing to the small left ventricle and at the level of the three vessel view, there's some retrograde flow present in the aortic arch.

The case on the bottom is a tetra of fallot.

The arrows are pointing to the overriding aorta and the three vessel view demonstrates a very large aorta with respect to the smaller main pulmonary artery.

So certainly possible to do here are two trisomy 21 fetuses, both at 12 weeks with subcutaneous edema hydrops fatalis and the arrows are pointing to large defects in the AV valves.

So AV septal defects.

This last case is one of absent ductus osis at 14 weeks and we can appreciate that the umbilical vein is connecting directly to the right atrium so that it is coursing abnormally through the body.

So, this is a very exciting future direction, the possibility that we may improve our detection rates by doing fetal echocardiography a little bit earlier in time.

This is a image from Poo at AL'S article where they demonstrated a nine week, spina bifida.

And I think that this is a pretty dramatic resolution coming back even before the 11 to 14 week examination.

And similarly in that article, there was some discussion about Mr.

Microscopy where they were, fixing specimens of human embryos and performing Mr microscopy.

And as you can appreciate here, the detail is exquisite.

This sort of knowledge is going to require us to truly understand anatomy and embryology.

And we have the potential with sono to perform sono embryology.

We can take volumes of these fetuses, slice 'em up and exactly correspond them to these MR images in order to advance our learning of embryology as it appears in ultrasound and perhaps even take diagnosis earlier, back in time.

Conclusion

So in conclusion, in many ways it's anatomic evaluation.

Anytime screen and diagnosis are rapidly shifting into first trimester, we have an ability to see more earlier, we're improving our understanding of embryology, but we have by no means, done away with the 18 to 22 week examination.

And there are enormous differences in results between groups at this time.

So we hope to increase knowledge and standardization over the coming years.

Thank you very much.