Babies with thumb duplication (or thumb polydactyly)
are born with an extra thumb on one or both hands. The two thumbs on one hand can
be joined or webbed together.
A thumb duplication is more of a split thumb rather than an "extra thumb."
When it affects one hand, both thumbs on that hand are usually smaller and less developed
than the thumb on the hand that is not affected.
What Causes Thumb Duplication?
Thumb duplication happens before a baby is born. When a baby's hands are first
forming, they are shaped like mittens. Then the fingers split. An extra split can
result in thumb duplication. The reason this happens is not known. It is not caused
by anything a mother did or did not do while pregnant.
Who Gets Thumb Duplication?
Any baby can be born with thumb duplication. It sometimes runs in families. Most
babies who have thumb duplication do not have other health problems. But sometimes,
thumb duplication happens as part of a genetic
How Is Thumb Duplication Diagnosed?
A prenatal ultrasound
might show a thumb duplication. Otherwise, doctors diagnose it when a baby is born.
X-rays of the bones in
the thumbs and hands will help the surgeon decide on the best kind of treatment.
How Is Thumb Duplication Treated?
Most babies with thumb duplication get surgery. The surgery removes the extra thumb
and, if needed, rebuilds the remaining thumb. The hand is usually put in a cast
for a few weeks after surgery.