Merck Manual

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Some Examples of Birth Defects

Some Examples of Birth Defects

Organ System

Birth Defect Examples*

What Happens


Hypoplastic left heart syndrome

Underdevelopment of the left ventricle, leading to inability to pump blood to the body

Separate operations to rebuild the left ventricle or a heart transplant

A hole in, or weakening of, abdominal muscles, allowing internal abdominal organs to spill out (protrude) through the defect

Surgery to close the defect

The foot and ankle are twisted out of shape or position

Immobilization with a cast and physical therapy to stretch the foot and ankle

Sometimes surgery


Brain tissue missing and replaced with fluid-filled sacs

No treatment available

Ventricular shunt may decrease pressure

The bones of the spine (vertebrae) do not close over the spinal cord

Surgery to cover the opening

A testis (testicle) remains in the abdomen or groin instead of descending into the scrotum before birth

About half will descend into the scrotum without treatment by 4 to 6 months

Surgery to move the testis into place

* These examples are only some of the many birth defects that can affect these organ systems.