In approximately 50% of children noted to have one or more congenital malformations, only a single malformation is identifiable; in the other 50%, multiple malformations are present. About 6% of infants with congenital malformations have chromosomal defects, 7.5% have a single gene disorder, 20% have conditions that are due to multifactorial effects (an interplay between genetic and environmental factors), and approximately 7% are due to exposure to a teratogen. In more than 50% of cases, no cause can be identified.
The history of the pregnancy and birth can reveal multiple riskfactors that are associated with dysmorphology. Small for gestational age infants may have a chromosome anomaly or may havebeen exposed to a teratogen. Large for gestational age infantsmay be infants of diabetic mothers or have an overgrowth syndrome, such as Beckwith-Wiedemann syndrome. When evaluating an older child with intellectual disabilities, complicationsof extreme prematurity may account for the child’s problems.Postmaturity also is associated with some chromosome anomalies (e.g., trisomy 18) and anencephaly. Infants born from breechpresentation are more likely to have congenital malformations.
As a woman gets older there is increased risk of nondisjunction leading to trisomies. Advanced paternal age may be
Brachycephaly: Condition in which head shape is shortened from front to back along the sagittal plane; the skull is rounder than normal
Canthus: The lateral or medial angle of the eye formed by the junction of the upper and lower lids Columella: The fleshy tissue of the nose that separates the nostrils Glabella: Bony midline prominence of the brows
Nasal alae: The lateral flaring of the nostrils Nasolabial fold: Groove that extends from the margin of the nasal alae to the lateral aspects of the lips
Ocular hypertelorism: Increased distance between the pupils of the two eyes Palpebral fissure: The shape of the eyes based on the outline of the eyelids
Philtrum: The vertical groove in the midline of the face between the nose and the upper lip Plagiocephaly: Condition in which head shape is asymmetric in the sagittal or coronal planes; can result from asymmetry in suture closure or from asymmetry of brain growth
Scaphocephaly: Condition in which the head is elongated from front to back in the sagittal plane; most normal skulls are scaphocephalic
Synophrys: Eyebrows that meet in the midline Telecanthus: A wide space between the medial canthi
Brachydactyly: Condition of having short digits
Camptodactyly: Condition in which a digit is bent or fixed in the direction of flexion (a “trigger finger”–type appearance)
Clinodactyly: Condition in which a digit is crooked and curves toward or away from adjacent digits
Hypoplastic nail: An unusually small nail on a digit
Melia: Suffix meaning “limb” (e.g., amelia—missing limb; brachymelia—short limb)
Polydactyly: The condition of having six or more digits on an extremity
Syndactyly: The condition of having two or more digits at least partially fused (can involve any degree of fusion, from webbing of skin to full bony fusion of adjacent digits) associated with the risk of a new mutation leading to an autosomal dominant trait. Maternal medical problems and exposures (medications, drugs, cigarette smoking, and alcohol use) are associated with malformations (see Chapters 47 and 48).
An increased amount of amniotic fluid may be associatedwith intestinal obstruction or a central nervous system anomalythat leads to poor swallowing. A decreased amount of fluid maybe the result of a chronic amniotic fluid leak or point to a urinary tract abnormality that results in a failure to produce urine.