Low femur percentile but high AC & HC at 36 week growth scan!

[mpeps]

I am pregnant with a baby boy. I have been sent for growth scans due to my bump measuring big (I was measuring 41 at my 35 week midwife appointment). I attended a growth scan today and they picked up too much amniotic fluid (Polyhydramnios). However, the scan also picked up that the femur length is on the 4th percentile (it was on the 9th percentile at my last growth scan), head circumference is on the 90th (this has increased from 66th at my last growth scan) and abdominal circumference is on the 91st.

They have referred me for a consultant scan tomorrow.

I was diagnosed with gestational diabetes during my last pregnancy. Tests have come back negative so far for this pregnancy. My daughter was always measuring big for AC (99th percentile). Legs were short (about 16th), but not this short, and head was fairly average (slightly on larger side).

I'm really worrying as Google is giving me bad answers (dwarfism, trisomy etc). Has anyone had a similar situation?

thanks in advance xx

Did the sonographer raise any concern, or have you just reviewed the figures post scan on your own? If the latter, I wouldn't be concerned. These measurements all have a degree of error, and a tiny measurement difference can result in a big percentile difference. I was having very regular scans at one point during my pregnancy, and the percentiles often changed rapidly within each 2 week period - it was never raised as a concern and I did have some that were very low and others quite high.

Edited to say, do of course tell your midwife about your concerns to get more info/put your mind at rest. I'm not medically qualified but wanted to reassure that having these differing percentiles does not definitely mean there is a problem.

I had a 20 week scan where the femur was average- ~50th percentile. Head 50th, body 80th percentile.

I had a growth scan at 30 weeks due to reduced movement and femur was <3rd percentile, it was off the bottom of the lowest line! Head and body were both 75th percentile.

I worried. However I have since had a growth scan at 32 weeks and the head and body are still 75th percentile and the femur is now just above the 50th percentile! The doctor who I saw after this scan said femurs don’t grow like this and that it was likely an error, or someone new doing it. To be honest I had student sonographer take the measurements at 30 and 32 week scans. Since the second scan I’m now more reassured that it was an error or a bad angle for measuring the femur.

Could this be what has happened in your case? I guess you had 9th and now 3rd so it’s less extreme compared to my scan differences. However it could still be they don’t fully have a clear view of the femur?

My little DGS (now aged 3) had almost identical measurements... huge head, big tummy and 3rd centile legs. He was born looking short, square and big headed.
Fast forward three years and he is growing into his beautiful (but large) head, and he is a stocky little fellow. He IS short... 1st-2nd centile for height..his friends are literally a head taller. But perfectly normal.
His sister was born 3 weeks ago... identical measurements on the scan (fractionally smaller head) and we are guessing she's also going to be a short compact kid!
Hopefully the scans will not show anything alarming...kids do vary!

My baby's measurements always put his head and belly in 80-95th centile and his femur ranged from 3rd to 15th! He was born at 40 weeks and looks perfectly in proportion with his height on the 50th centile. After the femur measured 3rd centile I asked the doctor if I should worry, and he said 'you can, but it won't make his legs any longer'. Perhaps not very well put but honestly my baby seems fine and babygros etc all fit him well so I think the measurements for scans can just be wildly inaccurate. Don't panic!