#Fetal #Biometry on Ultrasound-Obs #USG Basic Series #DAMS #NEETPG #AIIMS



now there is a recent trend in many exams to ask basic ultrasound obstetric images nowadays especially if some of you appeared for the aims exam this time and you saw image in which they had anencephaly cystic hygroma as a choices so we atoms feed that we will be sharing a series of clinic or radiological videos with orbs ultrasound as the focus the first video in this series will be on fetal biometry how to measure basic parameters on antenatal ultrasound for biometric to begin with this I will divide this session into two parts one part will be dealt by me in which I'll deal with the technical aspects from the radiological aspect and other will be done by DP which you will be looking at the clinical significance of each parameter to begin with I want to look at the first parameter now the first parameter that we all should know which is very important for early fetal biometrics en el the word crl stands for crown rump length this is measured as the longest straight line measurement of the embryo from the outer margin of the cephalic pole for the rump of the embryo so let us look at this this is how you measure crl you take the one point of the cursor at the crown and we take a straight line to the rump this is crowned rump length very very important early pregnancy biometric marker and now I will ask come to titi to discuss the clinical significance of this parameter right so crown rump length as dr. semir said is a very important fetal biometry parameter in fact it is the best on some parameter for assessment of gestational age right now when we say that we should not only know this that this is the best parameter which holds at what times will be doing me crl assessment so the ideal time or the CRL assessment is between seven to ten weeks of gestational age and if we do it at this time why do we say it is the ideal time because the error or within which it gives you the values is going to be plus minus three days of the original gestational age so it becomes best parameter yes I did say that the ideal time is seven to ten weeks also remember it is to be used as the ulsan parameter for gestational age assessment up to 14 weeks which means up to 84 mm if they ask us what is the best ultrasound mark of a gestational age or up to 14 weeks what is the best mark of a gestational age the answer is going to be crl right now why do we say 84 mm because beyond this measurement the error rate goes higher so what should be used as a parameter beyond this so if the gestational age is more than 14 or the CRL is more than 84 mm then the parameter we should be using is BPD by title diameter right the second important thing that we should know about the relevance of crl is what what would be the smallest crown rump length at which the embryo is visible on the transvaginal ultrasound right so crl is seen on a transvaginal scan and then the CRL is as small as 3 to 4 mm and embryo can be appreciated on the vaginal ultrasound right the third important significance of crl is a crl of more than or equal to 7 mm I repeat a crlf more than or equal to 7 mm and you do not see a cardiac activity in the embryo right then this is one of the ultrasound markers off missed abortion right so crl more than or equal to 7 mm and no cardiac activity is the ultrasound criteria for mr. bortion the second ultrasound criteria for abortion is VG sac ms t ms t stands for mean shank diameter so g sac m is d more than or equal to 25 mm and you don't see a yolk sac inside so for m st or mean sac diameter the criteria is more than or equal to 25 mm and no yolk sac inside is the definition of abortion on ultrasound second is c RL more than or equal to 7 mm and you don't see a cardiac activity again a parameter for abortion on ultrasound so that was about the first parameter that we wanted to take up which is crown rump length let's look at the second parameter now the second parameter going into the correct sequence would be as we use actually is by proper a tail diameter BPD now the motion TPD you should have what other Sunbeam the fetal head should be perpendicular to the ultrasound beam you should see the head in an oval shape the thalamus should be available so we call this is by thalamic plane cerebellum an orbit should not be seen in this plane and km septum pellucidum should be visible and very important to realize we measure from the outer aspect of the bone to the inner aspect of the bone in the widest part let me show you so this is how the fetal head would look like it should look over and we should be at a perpendicular plane and you measure take the cursor at the outer part here and we continue the cursor till the inner part a this is how I measure the VPD and you can see the pelham eye and you can see the kom septum pellucidum now as same plane when we are at the whole shape of the head you can see the thala my cerebellum and orbits are not seen you can see the concept of velocity we also measure the head circumference very important to remember is head circumference is measured by measuring the circumference of the output part of the bone this is how you would measure the head circumference from the outer aspect now now what I request dr. JP to discuss the clinical significance of head circumference and biparietal diameter right we just said that the best parameter for gestational age is CRL but we also said that it can be used up to 14 weeks right so what do we use after 14 weeks now answer is going to be in the biparietal diameter and again what should we know the ideal time to use the BPD so the ideal time to use BPD as a mark of a gestational age is between 14 to 20 weeks right now I usually use the biparietal diameter so what is the relevance of its C or the head circumference the head ezio the head circumference becomes more reliable than the biparietal diameter when there is variation in the shape of the skull for example Dolokhov carefully or Braca carefully in these conditions it C would be a better parameter as compared to the biparietal diameter for the age assessment right now we will want to be third a fetal parameter the third parameter that is very important for us to for biometry is a femur length of the baby a PC we should say the full length of femur in the plane when we measure we have we should have the burn at perpendicular to the ultrasound beam the calipers should be placed at the junction of the bone and the cartilage and we should be measuring only the ossified bone and the caliper should not contain thee from the roll head in them let me show you the picture this is how you should see a long femur and you measure from one point to another excluding the femoral head excluding the cartilaginous part this is how you measure femoral femur length and I will now ask for the clinical significance so femur length would be the best parameter for gestational age in the third trimester so first trimester it with crl second trimester the better parameter is BPD although we can still measure the FL and in the third trimester the better parameter for gestational age would be femur length now please remember although I am saying that it is the better parameter in the third trimester you should know that you can visually is the femur as early as 10 weeks of gestational age right it is although not completely visualized but you can see it right now the other relevance is about the short femur so we might ask you guys seeing a short femur what should you think a short fimA can be a normal finding is well but more importantly we have to know that short femur is one of these soft markers of trisomy 21 or Down syndrome on ultrasonography right and if the femur is severely shortened so what is severely shortened if it is less than the 5th percentile that is required for that gestational age so if it is less than the 5th percentile it is severely shortened and if you see this severely shortened freedom' femur in the second trimester we must think in terms of either skeletal dysplasia or early onset intrauterine growth restriction in the baby right so this is what you should be knowing about the femur length right now please remember these three parameters are used for gestational age in case we do not or the questions do not specify the gestational age at which is it is done and we have to just choose the best parameter we have to understand two concepts the first concept is the best is crl the second concept that you have to know is the earlier you do the gestational age assessment more correct or close to the original value it is so whenever we answer questions these are the two things that we keep in mind so not only their correct timings but to know the proper assessment with least errors we have to do it earlier in the pregnancy and it will give you the best estimates right now now we have discussed three parameters out of that crl was the early biometric marker then we discussed for a second time prime-minister BPD's preferred biparietal diameter and for the third trimester we prefer femur length these are for the biometry for the gestational age assessment now I will show you a parameter which is assessed for fetal group which is which is the abdominal circumference now this is a very very important question you may get this question in any of your exams at what plane should you measure abdominal circumference whenever we measure the abdominal circumference we should see the following landmarks on the ultrasound image you should see the fetal stomach the umbilical vein and the portal sinus reason we have chosen is because these are this is the plane at which the liver is at its maximum dimension and you should keep the calipers at the skin's surface another point to remember is kidney and the cord insertion should not be visible in that plane once you understand this let me show you how it is seen so now this is I image showing your abdominal circumference this is the fetal stomach you can see the umbilical way and you can see the portal sinus you should see a hockey stick like appearance which is very important to identify the correct plane for abdominal circumference and as I have already mentioned it is the parameter for fetal growth and I will now request for the clinical correlation right so I now as compared to B P D F L or C RL AC is a slightly less predictive parameter for gestational age assessment especially in the early parts of the pregnancy it can't be used in the later part so what is the more important use of abdominal circumference it is the single best ultrasound marker for fetal growth which means the macrosomia as well as to look for intrauterine growth restriction right so it's the single best parameter with regards to macrosomia you have to know that the abdominal circumference of more than 35 mm is what is suggestive of fetal macrosomia right more than 35 mm and when you talk about a C and you talk about growth restriction we have to know that abdominal circumference is better on more sensitive for asymmetric IUGR as compared to symmetric i you g are right and this is what we do in IUGR babies as well we follow them up with ultrasounds and we follow them up with ultrasounds at an interval of 2 to 4 weeks very important AC should not be done before two weeks for follow-up the minimum gap should be two weeks so in mild cases we will do it at four weekly intervals while in severe cases we will do it at two weekly intervals now although yes we said AC is the single best parameter for fetal growth and hence for macrosomia but even better than AC is going to be we had LOX formula which is right there in front of you so had LOX formula uses the three parameters together which is the BPD the femur length and the abdominal circumference to give you the estimated fetal weight so again I will repeat for the fetal weight assessment or macrosomia the best would be had LOX but the single best charges on parameter is going to be dominant circumference right so I hope you make the best use of this video to identify these basic things whether they come as visuals or as concepts as MCQs right our purpose in this series of videos that we make in dams in teaching videos which are available on dams Lily channel on YouTube we would suggest if you can subscribe us on this channel and you would get automatic notification whenever we publish a new video our goal is to keep sharing information for this medium of Internet in social media so that you can learn some basics which are additional to the classes so our goal in this video wants to discuss basic retail biometry parameters and I hope we could make a difference in your understanding of the basic concepts thank you very much please look forward for more videos of us on dam CD channel thank you very much you

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