A congenital anomaly (also called birth defect, congenital malformation, or congenital abnormality) is defined as a structural or functional defect that is present at birth and different from what is considered normal. A structural defect is an abnormality in the structure of the parts of the body (skeleton and organs). Structural defects most often occur during the critical period of fetal development in the first trimester. Structural defects include heart defects, cleft palate, neural tube defects, club foot, and others. A functional defect is defined as a defect in how the body system works (eg, metabolic disorders, brain and nervous system problems, degenerative disorders, immune disorders, sensory disorders). This chapter will discuss only structural defects; functional defects are discussed elsewhere.
II. CLASSIFICATION OF ANOMALIES
Classification based on major and minor anomalies. An anomaly can be further divided into major anomalies that require medical and surgical care (eg, congenital heart defects, anencephaly, gastroschisis, cleft lip/palate, meningomyelocele) and minor anomalies that do not have medical significance (eg, single palmar crease, epicanthal folds, fifth digit clinodactyly). Approximately 75% of newborns with major congenital anomalies present with an isolated anomaly, and approximately 25% have more than 1 major anomaly. Neonates can have both major and minor anomalies.
Classification based on developmental process. Congenital anomalies can be classified based on the developmental process involved in their formation and may be described as malformations, deformations, disruptions, dysplasias, syndromes, associations, or sequences (see Table 93–1 for definitions). It is also important to understand that these may not be entirely mutually exclusive.
Approximately 3% of all newborns have a congenital anomaly in the United States, and worldwide, approximately 6% of all newborns have a congenital anomaly. Approximately 0.7% of infants have multiple major anomalies. The most common congenital anomalies are congenital heart defects, neural tube defects, and Down syndrome. Congenital malformations account for 20% of the cases of neonatal deaths.
IV. CAUSES OF CONGENITAL ANOMALIES
Causes of congenital anomalies include genetic causes (chromosomal disorders, single-gene defects, autosomal dominant or recessive inheritance, and others), maternal conditions during pregnancy (infections, chronic maternal diseases, smoking, medications, poor nutrition, environmental factors, TORCHZ (toxoplasmosis, other, rubella, cytomegalovirus, herpes simplex virus, and Zika virus), hyperthermia, alcohol and drug use), multifactorial causes (genetic plus environment), and unknown etiologies.
V. GENERAL APPROACH TO DIAGNOSIS
In the management of congenital anomalies, the neonatologist must deal with complex clinical issues calling for a wide range of diagnostic skills. Identifying the correct unifying diagnosis related to the congenital anomaly can help guide management, ensuring that interventions are appropriate and effective. This also facilitates realistic counseling about prognosis and recurrence risk. Only a few common syndromes associated with multiple congenital abnormalities are life-threatening in the neonatal period. It is important to note, however, that congenital malformations are the most common cause ...