Transcript
A (0:00)
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B (0:31)
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C (1:06)
Yes. Oh yes. In your face. In your face. What annoying thing is happening now? They're playing Diagnosis Jeopardy. When you win, you get to gloat. It's so stupid. So there is a reality that we kind of do stupid things sometimes as medical students, as residents, even as attendings. Like Medical Jeopardy. Well, well, that was out of Scrubs, not a sponsor. But the idea is sometimes it's good to just rehash some diagnostic issue or dilemma because it's actually a good learning case. That's what we're going to tackle in this episode. We're going to talk about the isolated finding of a fetal abdominal circumference greater than the 90th percentile. Now, let me clarify here. This is assuming that the normal view shows a normal anatomy, normal structures. All right. We published, I think it was in 2016 or 2017 where a patient presented like I think she was 34 or 35 weeks with absent fetal movement. The baby looked flat on the monitor. Of course. We put on an ultrasound to try to find a maximal vertical pocket and lo and behold, we didn't see diaphragmatic excursion and the abdomen was almost filled solid tragically, with this echogenic just, you know, mass. It ended up being, of course, a very large liver that was full of metastases because the fetus in utero had metastatic neuroblastoma. We published that when she presented as decreased fetal movement. So tragic. So for this episode and what we're trying to set up here, let's assume that the abdominal circumference is greater than 90 percentile, as it was in that example I just gave you. However, the abdominal contents looks normal. All right, so let's exclude anything, you know, odd and rare going on. Just an isolated abdominal circumference. Anatomy is otherwise normal. All the other parameters are less than 90. But the fetal abdominal circum is greater than 90. What is the diagnosis? So we're gonna talk about what is a diagnosis here. Now, let me flip the script here. We know that an isolated abdominal circumference under 10th percentile as an isolated finding is good enough for fetal growth restriction. You don't have to have the composite EFW all be under 10%, even though that also is a diagnosis of FGR. But just the isolated abdominal circumference under 10% by itself is diagnostic of FGR. So is the rebuttal true? Is the opposite end of the spectrum true? If the abdominal circumference is greater than 90%, then is it possible that that is diagnostic of LGA? Yes. Oh, yes. In your face. In your face. What annoying thing is happening now? They're playing Diagnosis Jeopardy. When you win, you get to gloat. It's so stupid. So that's what we're going to do. If you got that right, if you know the answer and you get it right, you get to gloat a little bit. But that's what we're going to tackle. What is a diagnosis for an isolated abdominal circumference greater than 90th percentile? What is the diagnosis? What is the diagnosis? Oh, my goodness. All right, I think I've set it up enough. We'll be right back. This is Dr. Chapman's OB GYN. No Spin podcast. What is the diagnosis? So it is true. An isolated abdominal circumference under 10th percentile. According to AIUM, ACOG and SMFM and the UK's NICE guidance, everybody agrees under 10th percentile is diagnostic of fetal growth restriction. Because the abdomen is the first to show signs of fetal growth restriction as glycogen stores in the liver, which makes up the majority of the fetal abdomen, become less than the abdomen first becomes 10 percentile. That's why you get a diagnosis. They get umbilical artery dopplers, they get surveillance, and then you have to follow the trends in weight to see if the entire EFW will drop then under the 10th percentile. Remember, we've covered this recently that although the abdominal Circumference of under 10 percentile is diagnostic, you don't base management based on The AC by itself, you do get surveillance, you do get umbilical artery dopplers, but delivery is based on the total efw. Okay, so that's where it gets a little confusing. So the abdomen is very sensitive, but it's not the most specific. That's why you've got to look at the EFW to make delivery decisions as well as umbilical artery doppler findings. All right, so the question is, and it's logical, well, if a small abdomen is fgr, then a big abdomen is lga. It makes total sense. So logistically that's correct. The problem is diagnostically that is not correct. So right now, as Of April of 2026, the national and international consensus is that you cannot diagnose fetal LGA simply based on an isolated AC of greater than 90th percentile. If the EFW is under 90th percentile by Hadlock or whatever other composite formula you use. The majority of us uses Hadlock. We've talked about that in the past as well.
