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Large head small femur 36 weeks - should I be worried?

(14 Posts)
worryingyetagain Wed 13-Apr-16 15:52:41

At my 20 week scan my baby had large head measurements (around 90th centile) but the femur length and abdominal measurements were average (bang on 50th).

I've had other scans since then for various reasons, at 28, 34 and 36 weeks. Looking back at the scan reports the baby's head measurements have always been on the large side, the abdomen always around average but the femur, while still growing, seems to be falling further and further behind.

At the 36 week scan the head measurements were 90th centile and the femur only 10th. I discussed it very briefly with the sonographer and he wasn't worried because the measurements were still increasing and were in normal range.

Now I've googled (bad idea) and am panicking having read about this being a marker for DS and dwarfism. I also noticed that the amniotic fluid level was relatively high at 34 weeks (90th centile ish).

Anyone have anything similar? Am I worrying unnecessarily or should I be concerned? Help please!

MyNewBearTotoro Wed 13-Apr-16 16:34:00

I'm sorry I haven't experienced anything similar but I would feel reassured that your sonographer wasn't worried. They will have been trained to look for markers of conditions such as DS and dwarfism and what kind of ratios, percentiles or increasing/ decreasing growth patterns most commonly indicate a problem. So whilst they can't do so with 100% accuracy I would guess they will have been looking to spot anything that might suggest your baby isn't okay and so if they think it's nothing to worry about it probably isn't.

That said if you are genuinely concerned and worrying about this maybe it is worth discussing it with your midwife who can either put your mind at rest or, if she also feels it could indicate a problem, refer you for another scan.

Mrsmulder Wed 13-Apr-16 16:37:56

My ds was measuring small on his femur measurements, I asked my consultant about it because I was worried and he laughed and said it means he might have little legs. His legs were on the shorter side but not noticeably so. He now wears the correct size trousers for his age so I assume his legs are average size now

FemaleDilbert Wed 13-Apr-16 16:45:56

My son was pretty much exactly how you described - measurements wise. I also had polyhydramnios (too much fluid). My son is now 2, totally normal, bit shorter than average but well within 'normal' range

worryingyetagain Wed 13-Apr-16 17:29:33

Thanks so much for the responses. mrs and female it's reassuring to know you had similar measurements and all was fine.

It seems so odd to me as DH and I are both average height, neither particularly short. And I can't get over the head/femur ratio, I read on some website or other that it was a bad sign...

Argh I wish I could stop worrying. mynew I'm wondering about phoning but it's so late in the pregnancy now anyway.

SolomanDaisy Wed 13-Apr-16 18:52:52

I'm 5'6" but have really short legs. DS inherited this, along with my Dad's massive head. I can't remember his femur measurement, but I remember it suggested short legs, and his head was 98th percentile! He's actually very tall for his age, but has short legs (and a big head).

worryingyetagain Wed 13-Apr-16 22:34:25

soloman yep, to be honest the more I think about it the more I realise that's kind of me too...I have quite a big head blush and short legs with a long torso. I'm also 5'6".

Do you think I can be reassured that the femur is still on the 10th centile, at least? My hospital doesn't seem to worry unless it's under 5th or over 95th. But I'm conscious that I'm now v close to those in both directions.

Sigh. I never realised I'd worry so much in pregnancy.

worryingyetagain Thu 14-Apr-16 08:22:51

Bumping just in case...

KatharinaRosalie Thu 14-Apr-16 10:15:30

those scans are very inaccurate. I had one I think at 36 weeks, where they told me DD had 98th percentile head. She was born with a slighly below 50th one.

worryingyetagain Thu 14-Apr-16 11:14:31

Thanks Katharina. There seem to be so many stories like that, it's amazing how far off the mark the measurements can be! Ultrasounds are amazing in some ways but they're obviously not foolproof.

I'm trying really hard to keep busy and not go too far down the rabbit hole. But I found a study which said that the slowing down of femur growth after 25 weeks, plus the larger than average head, can be a marker for achondroplasia (most common form of dwarfism). It worried me a lot.

SerBronn Thu 14-Apr-16 13:55:14

Id try not to worry, especially if the sonographer wasn't concerned. When I was pregnant with DS I had to have a bunch of growth scans, on all of them he had really short femurs (literally at the smallest end of the scale) and a giant head. When he was born his head circumference was 1 or 2cms from being 'too big'. He's 2.5 now, still has short legs but none of the family are particularly tall and his head doesn't look too big for him and he's totally healthy smile

BigBroIsWatching Thu 14-Apr-16 14:09:14

My son had a head on a similar percentile and Femur, not so much.

He's now 7, above average in height and has a head of a 10 year old! But I have a larger head, and hats are rather snug. So it's just his body shape.

The scans work in MM. If the scan is a couple of MM out, imagine how skewed the results could look.

Remember, the percentiles are what's normal. Your son is within the normal range for everything.

My current pregnancy, my baby was towards the bottom end for everything. I worried, and panicked about her having Dwarfism etc then realised that the person doing my scan was a Fetal Medicine Specialist, as I was under consultant care for something else, and he would se le abnormalities daily compared to what I would see. So any concerns would have been raised and another scan brought forward.

Please don't worry. Of course, speak to your midwife to reassure you, but I am certain they would have highlighted any concerns at past scans.

sandy30 Thu 14-Apr-16 16:31:08

Same as my son. He has just inherited my mahoosive head and stumpy legs..

ShowMeTheWayHome Wed 01-Mar-17 09:32:34

Hi, can you please let me know how you got on? Was everything ok with your baby? I'm in a similar position and really worried. Thanks

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