What are congenital hand differences? Babies born with hands
that are different than the normal hand have a congenital hand
difference. What causes congenital hand differences? The upper
limb is formed between four and eight weeks after the sperm and
egg unite to form an embryo. The embryo develops an arm bud at
four weeks. The tip of the arm bud sends messages to each cell
as the upper limb forms. Millions of steps are followed to form
a normal arm. Failure of any of these steps to occur can result
in a congenital hand difference. Research continues into further
understanding of this embryonic process. Some congenital hand
differences may occur due to a genetic cause. Many congenital
hand differences just occur without an apparent cause. What are
different types of congenital hand differences? One in twenty
children is born with some difference from normal, either major
or minor. The different groups of congenital hand differences
include missing parts of the arm (failure of formation), webbed
or fused parts