26 week ultrasound results questions

[sletcr]

Hi!  I just had a 26 week ultrasound at 26 weeks and 3 days.  My results were as follows:

FW 880grams, FW% 28, BPD 62mm, FL 46mm, HC 237mm, AC 223mm, HC/AC 1.06, don't have humerus bone measurement but  know it was 25.4% which was normal.

My perinatologist said that everything looks good right now except the femur bone was a little on the small side of normal - 8% especially when compared to the AC.  He is not worried and said it's not a marker for Down Syndrome but I am worried. Is this femur length ok?  How much in the normal range is this measurement?  Also, as compared to the other measurements.  He tested my thyroid yesterday just to make sure all is well in that area but is not concerned about the measurements otherwise.  Wish I could say the same for me!

Thanks for your help!

Stacy

[sasex]

A related discussion, Here are some norms was started.

[sletcr]

Hi Dr. Brown,

Thank you for your answers.  I really appreciate the insight.  It so worrying getting all these measurements month after month, especially if something seems out of line a little bit.  I will have another scan in 4 weeks.  I am a lovenox patient due to a prothrombin and mthfr gene mutation so I am watched closely.

Quick question.  You mentioned that the arm bone (humerus) is consistent with the leg measurement.  How is that if the arm bone is in the 25% but the femur is in the 8%.  Did he mean that the femur was 8% as compared to the AC but alone as a measurement against gestational age it's higher?  Just curious.  Also, at my 12 week NT scan she was measuring a full 7 days ahead (which was surprising to me) so they moved my due date up a week.  Could it be that if my due date hadn't been moved, than she wouldn't seem as small week wise?  

Thanks again for everything!  By the way, I am only 5'1 and my husband 5'5 so I didn't think this baby would be tall but my perinatologist is very conservative and likes to get everyone as close to 50% as possible.

Thanks!

Stacy  

[Elaine Brown, MD]

Hi!
The bad news is that you never get to stop worrying about them -- I thought after they were born it would be better -- not!

The good news is that femur length is often small, and most often this is due to "technique".  In other words, it is difficult to measure the leg because the babies move around a lot, so sometimes the measurement is not accurate.  If it is accurate, the most common reason is that mom and dad are not NBA stars.  If the parents are not tall, the baby probably won't be either, but this is not an abnormality, just a family trait.

By the way, humerus is the arm bone.  The measurement of the arm is consistent with the leg measurement.  I suspect that your doctor will do a follow up scan, and the measurements may be quite different next time.

Hope this helps!
Dr B