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Do short HUMERUS, FEMUR in pregnancy indicate DOWN'S?

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I have a question about a second trimester ultrasound (23 weeks) that showed small long bones in one of my fraternal twin fetuses (the male fetus). Measurements were FL is 34.8mm, HL is 32.7mm. All other aspects of the ultrasound were normal- brain, heart, kidney, and bowels looked good/normal. First trimester ultrasound (12 weeks) showed nuchal translucency at 1.10 and 1.50, and the nasal bone was present/visible in both fetuses. Blood work for first trimester scan was- free beta hCG 42.90 IU/I, .751 MoM; PAPP-A .850 IU/I, .197 MoM. The ultrasound doc said the blood work pointed to a small increase in the risk for trisomy 18 (not 21), but added that with twins, blood work is not reliable/predictive.

During the second trimester US, the doc said the short long bone lengths raised the Downs risk for the male fetus from appox 1/2,700 to 1/28. That was less than welcome news. My wife is 30 years old patientold. We have decided against amnio, as we plan to keep both babies regardless.

Can you put the above into perspective (more than statistical risk) for me? Do you consider short humerus and femur one marker, or two?

Category: OBGYN

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Category: Infertility Specialist
 21 Doctors Online

Thanks for posting your query at
The best way of putting these findings into perspective is actually statistical risk.
Objectivity is better than pedantism in these cases.
Short humerus is a mid level marker, that, if present, raises the risk by 6 folds, and a short femur is a low level marker, that approximately raises the risk by 2.2.
So there are two soft markers , not one.
And a risk of 1 in 28 warrants an amnio, which again, is not essential, if termination is not an issue at all.
Not knowing for sure however, certainly is.
Short of an amnio, nothing can put this into absolute perspective.
Now you are the sole deciders of whether you wish to go ahead with that or not.
I would just state scientifically, that the risk if quite high, and it does warrant an amnio, however if you wish to continue anyway, the risks of an amnio outweight the benefits.
All the best
Please feel free to discuss further,

Dr. Aarti Vazirani
Category: Infertility Specialist
Residency: Obstetrics & Gynecolog, BJMC,Civil hospital, Ahmedabad, 2008
Post Graduate: MS (Obstetrics & Gynecology), B.J. Medical College, Ahmedabad, 2008
Medical School: MBBS, B.J. Medical College, Ahmedabad, 2004
Dr. Aarti Vazirani and 4 other Medical Specialists are ready to help you

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