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Thumb Hypoplasia

What Is Thumb Hypoplasia?

Babies with thumb hypoplasia are born with a thumb that is smaller than normal, or with the thumb missing completely. Sometimes the bones of the wrist or arm are smaller or missing too. Thumb hypoplasia can happen on one or both hands.

What Causes Thumb Hypoplasia?

Thumb hypoplasia (also called hypoplastic thumb) happens before a baby is born. When a baby’s hands are first forming, they are shaped like mittens. Then the fingers and thumb develop. In babies with thumb hypoplasia, the thumb does not form completely. Thumb hypoplasia is not caused by anything a mother did or did not do while pregnant.

Who Gets Thumb Hypoplasia?

Any baby can be born with thumb

. Sometimes, it happens as part of a genetic


How Is Thumb Hypoplasia Diagnosed?

A prenatal ultrasound might show thumb hypoplasia. 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. Other tests might be done to see if the thumb hypoplasia is part of a genetic syndrome.

How Is Thumb Hypoplasia Treated?

The thumb is a very important part of the hand. Surgery is usually recommended to improve a small or weak thumb. If the thumb is missing, the index finger can be made into a new thumb (this is called


After surgery, occupational therapy (OT) and home exercises can help a child learn to use the thumb.

Looking Ahead

After treatment, most children with thumb hypoplasia learn to do all the usual things that kids do. Offer support as your child learns how to use his or her hands well.