Hi everyone, I’m 37+3 weeks pregnant with a baby boy and would really appreciate opinions on how concerning these measurements are for skeletal dysplasia, particularly achondroplasia.
All previous anatomy scans have been normal and NIPT was low risk. At 31 weeks, the detailed scan specifically documented normal bone anatomy, normal limb movement, normal hands and normal facial anatomy:
* FL 58.9 mm — 32nd percentile
* HL 49.6 mm — 10th percentile
* EFW 31st percentile
At around 35 weeks, a routine scan showed that FL was 64 mm (meaning it had dropped to 7th percentile, measuring 33+1).
Interestingly, a repeat scan at 36+6 reportedly had the femur measuring at 36+0 weeks (I don’t have the measurement in mm or the percentile, they didn’t give me the report).
Today at 37+3, we did another scan which showed unexpected results for femur and humerus length.
* FL 65 mm — <1st percentile on the ultrasound machine, measuring 33+4
* HL 56.8 mm — ~1st percentile, measuring 33+0
* HC 18th percentile
* AC 68th percentile
* EFW 2,955 g — 35th percentile
There were no reported abnormalities of bone shape/mineralization, hands, thorax, skull or facial anatomy, and fluid/Dopplers are normal.
My husband and I are both of pretty average height (5’5 and 5’10).
My OB said skeletal dysplasia is possible but unlikely and is referring me to fetal medicine next week. He also mentioned that measurement variability is common this late in pregnancy, particularly given the discrepancy between the last two scans.
For those who are familiar, how is a pattern of isolated late-third-trimester shortening of the femur and humerus generally interpreted? Is this a pattern commonly seen with constitutional variation, or is late-onset shortening particularly characteristic of conditions such as achondroplasia?
Thank you!