Congenital anomalies are simply abnormalities of development that are present at birth. Location, magnitude, and mode of origin differ.They constitute about 80% of surgical problems in the newborn.

Cause

Congenital anomalies are the result of three basic causes: Dabnormal genes or chrotnosomes of the sperm or egg: abnormalities that develop in previously nornal genes or chromosomes (mutations) often because of noxious environmental influences; and unfavorable environment that prevents normal development of the fetus without any detectable chromosome or gene alteration.

Incidence

Over 25% of stillbom babies have congenital anomalies that caused the stillbirth; 3% of live babies are found to have congenital anomalies on immediate careful examination, and an additional 4% harbor occult abnormalities. Fortunately, most of these are minor and do not significantly affect growth, development, or life expectancy; 75% are single, but 25% are multiple-thus when one congenital anomnly is discovered in a baby, others must be anticipated. Anomalies are about 15% higher in males than in females. The incidence is 2. 5 times bigher in multiple than in single births. When one anomalous child is born into a family, there is a 25 times greater chance that subsequent children will have anornalies than if previous siblings were normally developed. With two malforned siblings in a family, there is about a 50% chance that the anomalies will be similar in location and severity. The central nervous system, cardiovascular, skeletal, and intestinal systems appear to be rost commonly involved in abnormal development.

History

The history is most important in diagnosing congenital anomalies, with the preceding causes being kept in mind. Questions should be directeded to anomalies in previous generations and the maternal health and habits during the pregnancy.

Abnormalities of amniotic fluid volume ( polyhydramnios is excessive volume; oligohydramnios is too little fluid) are frequently associated with fetal anomalies and should be investigated carefully by midtrimester prenatal amniocentesis and fetal ultrasound studies.

Normally the fetus continually swallows amniotic fluid from the fifth gestational month until delivery. This fluid is absorbed from the proximal small intestine to circulate as tissue fluid, plasma, and cerebrospinal fluid. It is then partially excreted through the placental circuit into the maternal circulation and partially excreted by the fetal kidneys buck into the amniotic sаc. Interruption of this cyclic flow at any point in the fetus ( proximal small bowel: atresia; central nervous system: anencephaly, hydrocephaly, myelomeningocele; urinary tract; atresia, renal aplasia) may upset the delicate balance of amniotic fluid to produce oligohydramnios or polyhydramnios.

Physical Examination

Physical Examination must be meticulous and detailed. It should include inspection of the freshly cut umbilical cord to see whether one of the umbilical arteries is missing; this often is a clue to the presence of a hidden anomaly in the body. Small catheters passed into both ends of the gastrointestinal tract can allow rapid diagnosis of obstruction. Special tests are listed under specifc congenital anomalies.

Treatment

The treatment of congenital anomalies must be individualized. No treatment is possible if the anomaly is so serious as to be immediately lethal or incorrectable, and none is necessary if the anomaly is so minor as to produce no significant change in function. Important aspects of the more common congenital anomalies are summarized in Table 39-1.

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