Re: mid-term femur length trisomy risk query
From: Allen Worrall (jworrall@alaska.net)
Thu Nov 17 08:21:54 2005
Dr. Smeltzer, thanks very much for this note. This note is one of those
things that is worth framing and posting at one's desk.
I also have had the experience of scanning a fetus that I knew had trisomy
21, and not being able to find a thing wrong with the fetus.
--
Allen Worrall
Joseph A Worrall MD RDMS
OB/GYN Ultrasound at the Fairbanks Clinic
Fairbanks, AK 99701
http://www.obgynsono.com
>----- Original Message -----
From: "James Smeltzer" <James.Smeltzer@wellstar.org>
To: "Multiple recipients of list ULTRASOUND" <ultrasound@dns.obgyn.net>
Sent: Thursday, November 17, 2005 3:58 AM
Subject: Re: mid-term femur length trisomy risk query
> Hi!
>
> Bernacerraf's group has studied this extensively. The use of isolated
> single measures to positively predict Down's Syndrome sonographically is
> not reliable, except the positive predictive value of atrioventricular
> septal defect (Downs vs field 2:1), duodenal atresia or web (1:2). The
> physiognomy, body type, arms, legs, hands, feet of a fetus should always
> be referenced to parents if possible, but very short is high risk, even
> with short parents IMHO.
>
> The problem is that a 40 y/o woman has a prior risk of 1/50, change to
> about 1/200 by nuchal lucency.
>
> Please check and comment on:
> nose bone (missing or small very common, upturned common),
> head shape (brachycephalic very common),
> ear length (short, low, simple very common),
> facial appearance especially mid-face projection (flat extremely
> common) and
> overall shape (round very common),
> current nuchal thickness (thickened common),
> humerus length (short very common),
> digits hand: (simian crease reported, but I have never seen it)
> (phalanges graduated stacked box appearance very common), especially 5th
> finger (clinodactyly with small and wedged MP of 5 is very common) and
> 1st toe (wide space very common), (short, wide feet very common),
> four-chamber heart, especially atrial dimensions of right vs left
> (right predominance in 85% by DeVore very common) and crux (straight
> across or missing in AV canal 5% but highly predictive), other heart
> defects effusions or hydrops (common - 50%, but less prenatally),
> umbilical artery (single uncommon but predictive),
> stomach appearance (double bubbles uncommon but predictive: one-third
> have DS),
> kidney appearance (renal pelvis dilation, mild common),
> bowel appearance (bright occasional but predictive),
> pelvis width (wide max outer to outer ilial diameter vs femur length
> common) and angle (>45 degrees, not reproducible by some common).
>
> We are starting on the wrong end of this equation, IMHO. People not
> only come in all shapes and sizes, they also have all kinds of
> dispositions.
> Do they wish prenatal diagnosis? If not, you are done unless there is
> a gross heart or other defect or hydrops.
> Is targeted imaging and expert counselling available? If so, they need
> it.
> Do they wish certainty regarding chromosomes? Is she losing sleep over
> this? Would she have an abortion? If so, needs amniocentesis.
>
> I will never forget the 35 year-old woman I cared for years ago in St.
> Louis. Missouri medicaid would not pay for prenatal genetic diagnosis.
> My chief, the late honorable Klaus Staisch, believed that providing this
> service was standard of care even in an indigent care hospital. The
> hospital ate the $700 a pop that Jim Crane charged us for the
> chromosomal evaluations - no discounts. You better believe we provided
> structured counselling. This woman desired amnio despite a negative
> sonogram. The results returned trisomy 21. I rescanned her with the
> results in hand, and the sonogram was normal. She carried the
> pregnancy. When the baby was born, I asked Corinne Valentik, our
> neonatologist, if the baby had a heart defect I had missed. SHe asked
> "What baby?" I said the one with Down's. She said that there was no
> baby in the nursery with Down's. I pointed the baby out to her and she
> said the baby did not have Down Syndrome: there was no sign of Down
> Syndrome. I said I had known that for five months, but it did not
> change the chromosomes. She was so skeptical she repeated them in a
> different lab. The results were the same, Trisomy 21.
>
> That baby taught me that dysmorphology only goes so far. The number
> and appearance of chromosomes is a fact. When you are only interested
> in that fact, the chromosomes are the things you should look at. When
> we can consistently and accurately harvest fetal cells at reasonable
> cost from maternal blood I will be out of that business. Until then, I
> enjoy the prenatal diagnosis and am happy that so far this is the only
> miss so far, and that my positive amnio rate for chromosomal
> abnormalities is between 20 and 35 percent. But I will never have a
> problem doing an amnio when the patient wants this certainty.
>
> "When all you have is a hammer, everything looks like a nail" ...
> (anonymous)
> ;^)
> Jim Smeltzer
>
> James S. Smeltzer, MD, FACOG, SMFM
> Consultant, Maternal Fetal Medicine
> Wellstar Physicians' Group
> Northwest Women's Care
> 787 Campbell Hill St
> Marietta GA 30060
> James.Smeltzer@wellstar.org
> VM 678-290-3035
> Off 770-528-0260
> Page 404-318-3451
>
>>>> fizztastic@talk21.com 11/15/2005 2:33:46 PM >>>
> The patient is 40 years old; her partner is 50. This is their first
> pregnancy. They are very concerned about age-related risk of
> chromosomal abnormalities, but opted against CVS and then amnio when
> 1st
> trimester screening adjusted their background trisomy 21 risk to 1:272
> and trisomy 13/18 risk to 1:843.
>
> The mother is above average height (183 cm) and the father is below
> average height (168 cm). Both are Causasian. My question is this: at
> 21 weeks + 3 (dated by known LMP), the femur length of the fetus is
> 33.5
> mm. (Other measurements taken at the same time include BPD 53 mm; HC
> 182 mm; TCD 21 mm; CM 5 mm and AC 161 mm.) Is this low enough to
> warrant
> concern? Urgently seeking advice. Any comments would be gratefully
> received. Thanks very much.
>
> Mary
>
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