Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. "Congenital" means "present at birth." (See also Introduction to Birth Defects of the Face, Bones, Joints, and Muscles Introduction to Birth Defects of the Face, Bones, Joints, and Muscles Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. "Congenital" means "present at birth." Birth defects of the face and limbs are fairly... read more .)
Birth defects of the muscles can occur alone or as part of a syndrome.
The pectoralis major muscle (the major muscle in the chest, sometimes called the "pecs" in adults) can be partly developed or missing altogether. This defect can occur alone or with various hand, breast, or nipple abnormalities, as in Poland syndrome. The cause of most of these types of muscle disorders is unknown.
One or more layers of the abdominal muscles may be missing at birth, as in prune-belly syndrome. In this disorder, the missing layers of abdominal muscles cause the abdominal wall to have a wrinkled appearance, the testes do not descend into the scrotum (cryptorchidism Undescended testes Undescended testes (cryptorchidism) are testes that remain in the abdomen or the groin instead of descending into the scrotum. Retractile testes (hypermobile testes) have descended into the... read more 
) in boys, and/or urinary tract defects develop. The cause of prune-belly syndrome is not clear.
Diagnosis of Muscle Defects
Before birth, ultrasonography
After birth, physical examination
Sometimes genetic testing
Before birth, doctors are sometimes able to diagnose these defects during an ultrasound Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more .
After birth, doctors can identify the defects during a physical examination.
Because abnormal genes may be involved in birth defects of the muscles, affected babies should be evaluated by a geneticist. A geneticist is a doctor who specializes in genetics (the science of genes and how certain qualities or traits are passed from parents to offspring). Genetic testing of a sample of the baby's blood may be done to look for chromosome and gene abnormalities. This testing can help doctors determine whether a specific genetic disorder is the cause and rule out other causes.
Treatment of Muscle Defects
Possibly surgery
Treatment of muscle defects depends on how severe the muscle defect is. The infant may need reconstructive surgery.
If an abnormal gene is found, families of affected children may benefit from genetic counseling.
