The Newborn Infant

General Appearance

Physical activity may be decreased by the effects of illness or drugs; an infant may be either lying with the extremities motionless, to conserve energy for the effort of difficult breathing, or vigorously crying, with accompanying activity of the arms and legs. Both active and passive muscle tone and any unusual posture should be noted. Coarse, tremulous movements with ankle or jaw myoclonus are more common and less significant in newborn infants than at any other age. Such movements tend to occur when an infant is active, whereas convulsive twitching usually occurs in a quiet state. Edema may produce a superficial appearance of good nutrition. Pitting after applied pressure may or may not be noted, but the skin of the fingers and toes lacks the normal fine wrinkles when filled with fluid. Edema of the eyelids commonly results from irritation caused by the administration of silver nitrate. Generalized edema may occur with prematurity, hypoproteinemia secondary to severe erythroblastosis fetalis, nonimmune hydrops, congenital nephrosis, Hurler syndrome, and from unknown causes. Localized edema suggests a congenital malformation of the lymphatic system; when confined to one or more extremities of a female infant, it may be the initial sign of Turner syndrome (see Chapters 98 and 604 ).

Skin

Vasomotor instability and peripheral circulatory sluggishness are revealed by deep redness or purple lividity in a crying infant, whose color may darken profoundly with closure of the glottis preceding a vigorous cry, and by harmless cyanosis ( acrocyanosis ) of the hands and feet, especially when they are cool. Mottling, another example of general circulatory instability, may be associated with serious illness or related to a transient fluctuation in skin temperature. An extraordinary division of the body from the forehead to the pubis into red and pale halves is known as harlequin color change , a transient and harmless condition. Significant cyanosis may be masked by the pallor of circulatory failure or anemia; alternatively, the relatively high hemoglobin content of the 1st few days and the thin skin may combine to produce an appearance of cyanosis at a higher partial pressure of arterial oxygen (Pa o ₂ ) than in older children. Localized cyanosis is differentiated from ecchymosis by the momentary blanching pallor (with cyanosis) that occurs after pressure. The same maneuver also helps in demonstrating icterus. Pallor may be caused by anemia, asphyxia, shock, or edema. Early recognition of anemia may lead to a diagnosis of fetomaternal blood transfusion, erythroblastosis fetalis, subcapsular hematoma of the liver or spleen, subdural hemorrhage, or fetal-maternal or twin-twin transfusion. Without being anemic, postmature infants tend to have paler and thicker skin than term or premature infants. The ruddy appearance of plethora is seen with polycythemia.

The vernix and common transitory macular capillary hemangiomas of the eyelids and neck are described in Chapter 669 . Cavernous hemangiomas are deeper, blue masses that, if large, may trap platelets and produce disseminated intravascular coagulation or interfere with local organ function. Scattered petechiae may be seen on the presenting part (usually the scalp or face) after a difficult delivery. Slate-blue, well-demarcated areas of pigmentation called mongolian spots are seen over the buttocks, back, and sometimes other parts of the body in more than 50% of black, Native American, and Asian infants, and occasionally in white infants. These benign patches have no known anthropologic significance despite their name; they tend to disappear within the 1st year. The vernix, skin, and especially the cord may be stained brownish yellow if the amniotic fluid has been colored by the passage of meconium during or before birth.

The skin of premature infants is thin and delicate and tends to be deep red; in extremely premature infants, the skin appears almost gelatinous and translucent. Fine, soft, immature hair called lanugo frequently covers the scalp and brow and may also cover the face of premature infants. Lanugo has usually been lost or replaced by vellus hair in term infants. Tufts of hair over the lumbosacral spine suggest an underlying abnormality, such as occult spina bifida, a sinus tract, or a tumor. The nails are rudimentary in very premature infants, but they may protrude beyond the fingertips in infants born past term. Postterm infants may have a peeling, parchment-like skin ( Fig. 113.1 ), a severe degree of which may mimic ichthyosis congenita (see Chapter 677 ).

In many neonates, small, white papules on an erythematous base develop 1-3 days after birth. This benign rash, erythema toxicum , persists for as long as 1 wk, contains eosinophils, and is usually distributed on the face, trunk, and extremities (see Chapter 666 ). Pustular melanosis , a benign lesion seen predominantly in black neonates, contains neutrophils and is present at birth as a vesiculopustular eruption around the chin, neck, back, extremities, and palms or soles; it lasts 2-3 days. Both lesions need to be distinguished from more dangerous vesicular eruptions such as herpes simplex (see Chapter 279 ) and staphylococcal disease of the skin ( Chapter 208.1 ).

Amniotic bands may disrupt the skin, extremities (amputation, ring constriction, syndactyly), face (clefts), or trunk (abdominal or thoracic wall defects). Their cause is uncertain but may be related to amniotic membrane rupture or vascular compromise with fibrous band formation. Excessive skin fragility and extensibility with joint hypermobility suggest Ehlers-Danlos syndrome (see Chapter 679 ), Marfan syndrome ( Chapter 722 ), congenital contractural arachnodactyly, and other disorders of collagen synthesis.

Skull

The skull may be molded, particularly if the infant is the first-born and if the head has been engaged in the pelvic canal for a considerable time. Caput succedaneum , caused by scalp pressure from the uterus, cervix, or pelvis, appears as a circular boggy area of edema with indistinct borders and often with overlying ecchymosis. A cephalohematoma presents as a well-circumscribed fluid-filled mass that does not cross suture lines. Unlike caput succedaneum, cephalohematoma is often not present at delivery but develops over the 1st few hr of life. Both cephalohematoma and caput succedaneum must be distinguished from a subgaleal hemorrhage , which is not restricted by the boundaries of the sutures and therefore is larger and more diffuse. Subgaleal hemorrhage requires prompt recognition because extensive bleeding may result in hypovolemic shock, with estimated mortality up to 20%. The head circumference of all newborns should be plotted on a growth chart to identify an excessively small head ( microcephaly ) or excessively large head ( megalencephaly ). The diagnostic differential for microcephaly is broad and includes underlying genetic disorders, congenital infection, and intrauterine drug exposure (see Chapter 609 ). Megalencephaly can suggest hydrocephaly, storage disease, achondroplasia, cerebral gigantism, neurocutaneous syndromes, or inborn errors of metabolism, or it may be familial. The suture lines and the size and fullness of the anterior and posterior fontanels should be determined digitally by palpation. The parietal bones tend to override the occipital and frontal bones. Premature fusion of sutures ( cranial synostosis ) is identified as a hard nonmovable ridge over the suture and an abnormally shaped skull. Great variation in the size of the fontanels exists at birth; if small, the anterior fontanel usually tends to enlarge during the 1st few mo after birth. The persistence of excessively large anterior (normal: 20 ±10 mm) and posterior fontanels has been associated with several disorders ( Table 113.1 ). Persistently small fontanels suggest microcephaly, craniosynostosis, congenital hyperthyroidism, or wormian bones; presence of a 3rd fontanel suggests trisomy 21 but is seen in preterm infants. Soft areas ( craniotabes ) are occasionally found in the parietal bones at the vertex near the sagittal suture; they are more common in preterm infants and in infants who have been exposed to uterine compression. Although such soft areas are usually insignificant, their possible pathologic cause should be investigated if they persist. Soft areas in the occipital region suggest the irregular calcification and wormian bone formation associated with osteogenesis imperfecta, cleidocranial dysostosis, lacunar skull, cretinism, and occasionally Down syndrome.

Atrophic or alopecic scalp areas may represent aplasia cutis congenita , which may be sporadic, or autosomal dominant, or associated with trisomy 13, chromosome 4 deletion, or Johanson-Blizzard syndrome. Deformational plagiocephaly may be the result of in utero positioning forces on the skull and manifests as an asymmetric skull and face with ear malalignment (see Chapter 610 ). It is associated with torticollis and vertex positioning. Depression of the skull (indentation, fracture, Ping-Pong ball deformity) is usually of prenatal onset and a result of prolonged focal pressure by the maternal pelvic bone.

Face

The general appearance of the face should be noted with regard to dysmorphic features , such as epicanthal folds, widely or narrowly spaced eyes, microphthalmos, asymmetry, long philtrum, and low-set ears, which are often associated with congenital syndromes. The face may be asymmetric as a result of a 7th nerve palsy, hypoplasia of the depressor muscle at the angle of the mouth, or an abnormal fetal posture (see Chapter 128 ); when the jaw has been held against a shoulder or an extremity during the intrauterine period, the mandible may deviate strikingly from the midline. Symmetric facial palsy suggests absence or hypoplasia of the 7th nerve nucleus ( Möbius syndrome ).