18 week femur length 1mm short in U/S? (X-post to May 2012 DDC)

[rozziemama]

Hi everyone. I just posted this identical thread in my DDC but thought I might get some more input if I went more broadly... As I'm freaking out and will be checking obsessively for a reply 

So I normally hate to do this - post questions before I talk to my doctor - because it's almost always coupled with a wild irrational google search as well. So, I'm not thinking 100% rationally but I'm hoping to get some reassurance from this lovely group. 

I am 17 weeks 4 days today.  I went this morning for my "18 week" ultrasound.  Everything looked great, the heart, brain, palate, kidneys, nuchal fold was within the normal range... Images were amazing - the 3-D shot was something I never had with DS so we were in awe.  Baby was moving and yawning and pretty darn cute.

However, apparently the femur bone was measuring 1mm short.  OK, so I didn't think to ask what it was measuring at... And I also didn't understand what it was being measured against - could the "shortness" be due to me being 17.4 rather than a full 18 weeks? How significant is 1mm??  The Dr doing the scan said it was probably nothing since the other measurements were normal, but a short femur is a soft risk factor for Down Syndrome.  

Yes, so of course I'm in a tizzy. I mean, I hear the rational voice in my head saying "1) you aren't even 18 weeks yet and what's 1mm too short anyway, and 2) all other measurements are normal, so relax".  My gut tells me to relax. 

But I'm still totally freaked out. 

I don't know if anyone else out there has had a "short femur bone" for their fetus... I did some searching on the broader community pages, and I know I'm not going to feel better until I talk to my Dr and probably have another u/s in a few weeks ... still... any thoughts much appreciated...

[mamandedeux]

Same story here with DS1's 18 week (or maybe 20 week?) us. The dr. handed me the report saying everything was normal, but when I looked at it, the femur mesurement graph showed it was below the normal. I asked my dr. at the next prenatal and he said because everything else was ok, he wasn't concerned (I'd gotten the triple screen as well). Funny, he mentioned that DS1 would just never be very tall - he's 5 now and super tall. We call him slim because he's so lanky!!!  

Also, I remember reading that this is a hard measure to get, and that if everything else is ok, it could very well be a bad measurement.

Don't worry... (I know, I know.... impossible...)

[rozziemama]

Thanks so much for the reply.  I just got off the phone with the Dr's office ... they said "they've been getting a lot of results like this recently..." Now what the heck does that mean?!  I think it was supposed to make me feel better, but it doesn't because everything is such an unknown. They also told me that the femur measurement isn't a common marker unless it's taken with the nuchal fold, cardiac issues, etc. And all of those were fine. Ay yay yay. 

I didn't get the Early Risk Assessment... And now they are suggesting I just go in for the Quad Screen (?) -- but I'm kind of skeptical.. Seriously, this one unknown is freaking me out so much - and whatever probability I'm going to get means that there's always a probability in the other direction. And I am not sure if I'd do an amnio if it came to that unless the probability were really high... 

(but what does really high mean, anyway?!) 

I just kind of want to erase this whole experience. Makes me feel so sad and crazy and irrational. And google is my enemy. 

[mamandedeux]

I just went to double-check the measurements on DS1's chart. Femur length at 22 weeks was 31,2 mm. So waaaaayyyyy below normal, like 3 mm shorter. Knowing how paranoid it made me, I didn't even ask about the measurements for DS2. I asked the dr. to let me know if anything really worrisome showed up, if not, I didn't care to know.

Deep breath! You're good!

[rozziemama]

I've been wanting to go back and check DS1's measurements. Does the midwife/dr have that on file or did you actually take those measurements home with you?  I'm not sure how I'd be able to learn that info.

I finally talked to my dr yesterday. She said the femur length was 23 mm - which was normal for 17.5 weeks - but the ratio to the head was a little small. She agreed that it's very likely the head size was prob just big - runs in the family!  I'd feel A LOT better knowing what DS1's measurements were...

[mamandedeux]

I had to transfer care at 25 weeks, so I was given a copy of my chart. Get a copie at your next appt. Both my DSs have ginormous melons, above 90th percentile. Drs. always want to measure twice. My 5 y-o wears the same hockey helmet as my DH. Craaaazy!

[rozziemama]

I pushed my DS1 out for 5 hours and he had a ridiculous cone head at the end of it. He's tall and proportionate now but man, that head was big! 

[katt]

Babies grow at different rates.  Who said a specific length is normal?  

[rozziemama]

That is a good question. I think this is more about ratios between the different long bones/head size... and the growth chart ranging from 10% to 90%... my last Dr appt showed that the femur was at about 40%, the head at about 50% and the humerus at about 45%... Doesn't really seem so out of whack to me?!