Why is the length of the femur of my fetus short?

Q: My pregnancy corresponds to 27-31 weeks. The details of the USG report are - MY LMP: 27/11/05. USG details: BPD-76, FL-51, abdominal circumference: 239, head circumference: 261 and the fetal weight: 1.2 kg. The doctor says that the femur length seems to be small. Is it something to worry about? I am 4 feet 11 inches tall and my husband's height is 5 feet 4 inches. Please advise.

A:The head size and abdominal perimeter in this report correspond to 27-28 weeks size. The length of the femur is also within the normal range for this period, but is however, on the lower side of the normal range. This is expected when the parents are both in a similar height range, as in this case. To be doubly sure that this is a normal variant and not a disorder of bone growth and development, it would be wise to do a repeat ultrasound scan which includes an assessment of the length of all bones of all the limbs and also assess the overall architecture of the bones. This would confirm a normal variant and exclude a skeletal disorder.