Gupta et al identified several features in the limbs of a fetus which may indicate the presence of Down's syndrome. The authors are from St. Stephen's Hospital in Delhi, India.
Patient selection: mid second trimester onwards
Measurements taken during ultrasonography:
(1) forearm
(2) upper arm
(3) femur
(4) tibia
ratio of femur to tibia =
= (length of femur in mm) / (length of tibia in mm)
Parameter
Normal
Down's Syndrome
ratio of femur to tibia
1.1 (after 13 weeks gestation)
> 1.2 (after 20 weeks gestation)
tip of upper limb
to mid-thigh
to level of the pelvis
humerus
as predicted
shorter than predicted
forearm (ulna and radius)
as predicted
shorter than predicted
femur
as predicted
shorter than predicted
tibia
as predicted
shorter than predicted
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