Birth defects of the fingers and toes can occur while a baby is developing in the womb. For example, the baby may have too few fingers or toes. Or the baby may be born with extra fingers or toes.
In amniotic band syndrome, finger and toe defects (and other abnormalities) are caused when body parts are constricted by thin strands of tissue from the amniotic sac. The amniotic sac holds the amniotic fluid surrounding the developing fetus in the womb. The strands tangle around the fetus, like strings or rubber bands, trapping parts of its body and restricting growth of the body part.
Polydactyly is extra fingers or toes. The little fingers or toes and thumbs or big toes are the ones most commonly duplicated. The extra finger or toe may be just a nub of fleshy tissue or the extra finger or toe could be fully functioning, having its own nerve endings, bones, and joints.
Syndactyly is webbing or fusion of fingers or toes. In syndactyly, fingers or toes do not separate, producing a weblike hand or foot. In simple syndactyly, the soft tissues are fused together. In complex syndactyly, the bones and soft tissues are fused together.
Both polydactyly and syndactyly can occur on their own or as a part of a genetic syndrome such as Apert syndrome.
Before birth, doctors are sometimes able to diagnose these defects during an ultrasound.
After birth, doctors typically take x-rays and may do other imaging tests to determine which bones are affected. When defects seem to run in the child's family or if doctors suspect the child has a genetic syndrome, they also examine the child for other physical abnormalities and take a sample of blood to do genetic testing.
Surgery can be done to separate syndactyly of the fingers or toes and improve function. Surgery may be done to remove an extra finger or toe.
Some children who are missing a finger or toe need a prosthesis, which is an artificial device that replaces the missing body part (see Overview of Limb Prosthetics).