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35 weeks pregnant. Femur bone of foetus has not developed properly. Should I be concerned?

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Hi..I am 35 weeks pregnant, and since 18 weeks, have been detected with short long 18 weeks,it was 2 weeks short(22mm) and at 35 weeks, it is 5 weeks short(58mm). My measurement for 28 weeks was 45mm and for 32 weeks was 51mm.. However I have noticed that the percentage (of actual measurement/ideal measurement) is the same (around 80%-85% for all long bones). According to the fetal growth chart, the bones (femur) should have grown by around 39 mm since 18 weeks (to 35 weeks), and in my case it has grown by 36 mm.. (from 22 mm to 58 mm)...Is this a big concern?.. I am 5'2" and my husband is 5'4", and he has got very short this a reason? we did amnio at 18 weeks and all came out to be normal.
Also, could this be a case of dwarfism? Again, I checked some details online, and realized that in case of achon, the discrepancies are noted late in pregnancy and there is a big drop. In our case, the actual vs. ideal measurement in terms of % has been consistent. It was initially 77%, then became 83% and now at around 85%...Also, the BPD and HC are a few days behind. The AC is around a week and a half behind. There is no bowing, no frontal bossing, no trident fingers etc.
FL/AC ratio is 0.188

Please let me know if this is a matter of concern. Also, does this mean that the baby would grow up to be very short? Should I go for elective cesaerian? Is this a case of SKD? Is there a possibility that he has achon/hypochon?

Posted Mon, 5 Nov 2012 in Women's Health
Answered by Dr. Rakhi Tayal 1 hour later
Thanks for posting your query.
At 35 weeks of pregnancy all the limbs of the foetus are enough developed to comment about shortening of a particular long bone like femur. The shortening of femur is commonly associated with Down's syndrome. You have already tested negative for Down's syndrome.
Slight shortening of femur without any other anomaly in the fetus most commonly manifests as a short stature child but it is not necessary that the effect will be long lasting. Height of the child mostly goes after the family.
With good diet and proper protein and calcium supplements given after birth the child will catch up with the growth and might develop normally with a good height after one year of birth.
It is not necessary that this will show any long term effects on the baby. You can go for an elective cesarean delivery if there is an indication and is deemed necessary by your obstetrician. Since the femur size is 85% of normal and is growing with fetal age, achondroplasia or hypochondroplasia is ruled out.
Since there is no worsening of femur shortening with gestational age, skeletal dysplasia is also not likely.
Hope this answers your query. I will be glad to answer the follow up queries that you have.
Please accept my answer in case you do not have further queries.
Wishing you good health.
Dr. Rakhi Tayal.
Above answer was peer-reviewed by
Follow-up: 35 weeks pregnant. Femur bone of foetus has not developed properly. Should I be concerned? 2 hours later

Thanks for your reply. I understand that slight shortening is not a problem. But, I guess in our case, the shortening is considerable, or atleast that is what we were made to believe by the sonographer.

Well, from being 2 weeks behind in 18 weeks to 4 weeks behind in 28 weeks to 5 weeks behind in 35 weeks, it seems to be a big drop. Just because I have a love for statistics, I worked out the percentage thing myself, and realized the following:

18 weeks: ideal= 28 mm, observed= 22 mm, actual/ideal= 78.5% ( 2 wks behind; 10 percentile)
28 weeks: ideal= 54 mm, observed= 45 mm, actual/ideal= 83.3% (BUT 4 weeks behind; 3 percentile)
32 weeks: ideal= 62 mm, observed= 51 mm, actual/ideal= 82.2% (BUT NOW, 5 weeks behind; <2.3 percentile)
35 weeks: ideal= 67 mm, observed= 58 mm, actual/ideal= 86% (AGAIN, 5 weeks behind; <2.3 percentile)

Whereas the percentage is worked out by me, what is given in the reports are the "x weeks behind" thing, which is progressively increasing.... And apparently, that is what everyone looks at!!!!

Thing is...our obstetrician has left the option of going for an elective C-section to us, and also mentioned that one of the reason could be the possibility of SKD due to the short long bone thing. That is why I wanted to know is SKD can actually be ruled out.... What does your experience say?

Is what is happening with me normal? or grossly abnormal?

Thanks once again

Answered by Dr. Rakhi Tayal 13 hours later
Thanks for writing again.
Since the discrepancy in femur growth is gradually increasing in terms of weeks, SKD is a possibility. It is good that actual/ ideal percentage difference is decreasing thus suggestive of a progressive growth of femur. This makes SKD an unlikely possibility but it cannot be completely ruled out.
The short femur is a common finding but is not always associated with an abnormality. Please do not worry. There is a possibility of catching up of growth after birth.
Hope my answer is helpful.
Do accept my answer in case there are no further queries.
Above answer was peer-reviewed by
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