The newborn infant

Infants are usually born at term between 37 and 42 weeks of gestation. This time period can be further divided into early term (37 to 38 weeks), full term (39 to 40 weeks), and late term (41 weeks) deliveries. After 42 weeks of gestation, birth is considered postterm. Approximately 10% of births are preterm, occurring prior to 37 completed weeks of pregnancy. Most infants born at term require very little medical attention in order to successfully adapt to extrauterine life. Routine management of a newborn infant immediately after birth consists of removing airway secretions, drying the newborn, and providing him or her with warmth. Health care providers also clamp and cut the umbilical cord. The Apgar score is typically used to gauge the clinical status of newborn infants at one and five minutes after birth using the following parameters: heart rate, respiratory effort, muscle tone, reflex irritability to tactile stimulation, and skin color. Infants who are born at term or late preterm and are breathing and moving satisfactorily should immediately be given to their mother for skin-to-skin contact and initiation of breastfeeding. Infants who are born prematurely, lack muscle tone, or are not breathing or crying may require supplemental oxygen or neonatal resuscitation.

Preventive medicine measures in the delivery room include the administration of ophthalmic antibiotics and vitamin K. Within 24 hours of birth, a detailed assessment of the newborn should take place. This typically includes a history of the pregnancy and a physical exam from head to toe, as well as measurements of length and weight.

General

• Infant: a child under 1 year of age ^[1]
• Newborn: a child under 28 days of age ^[2]
• Perinatal period: the period from the 22^nd week of gestation to the 7^th day after birth ^[3]
• Postpartum period: first 6–8 weeks after birth
• Live birth: postnatal presence of vital signs (e.g., respiration, pulse, umbilical cord pulse) ^[4]

Timing of birth ^[5]

• Term birth: umbrella term for live births between 37 and 42 weeks of gestation
  • Early term infant: live birth between 37 0/7 weeks and 38 6/7 weeks of gestation
  • Full term infant: live birth between 39 0/7 weeks and 40 6/7 weeks of gestation
  • Late term infant: live birth between 41 0/7 weeks and 41 6/7 weeks of gestation
• Preterm infant: live birth between 20 0/7 weeks and 36 6/7 weeks of gestation ^[6]
• Postterm infant: live birth after the 42^nd week of gestation

Evaluation of birth weight

• Appropriate-for-gestational-age infant (AGA): birth weight 10^th–90^th percentile for gestational age
• Small-for-gestational-age infant (SGA): birth weight < 10^th percentile for gestational age ^[7]
• Large-for-gestational-age infant (LGA): birth weight > 90^th percentile for gestational age
• Low birth weight ^[8]
  • Birth weight < 2,500 g regardless of the gestational age
  • Occurs in early term infants and infants with intrauterine growth restriction
  • Associated with increased mortality, particularly due to sudden infant death syndrome
  • Very low birth weight: birthweight between 1,000–1,499 g regardless of the gestational age
  • Extremely low birth weight: birthweight < 1,000 g regardless of the gestational age

Pregnancy loss

• Miscarriage (spontaneous abortion)
  • Absence of vital signs
  • Pregnancy loss before the 20^th week of gestation
  • Fetal weight less than 500 g
• Stillbirth (fetal death)
  • Absence of vital signs
  • Most US states report fetal death if pregnancy loss occurs during or after the 20^th week of gestation
  • Fetal weight more than 500 g

Immediate care of the newborn

• Wipe the newborn's mouth and nose to clear airway secretions, use suction only if necessary.
• Dry and stimulate the newborn.
• Provide warmth.
• Skin-to-skin contact with mother and initiation of breastfeeding
• Clamp and cut the umbilical cord.
• Apgar score assessment at 1 and 5 minutes after birth
• Begin resuscitation if onset of respirations has not yet occurred within 30–60 seconds

Apgar score ^[9]

• Used for standardized clinical assessment of newborns at 1 and 5 minutes after birth
  • Five components: skin color, heart rate, reflex irritability to tactile stimulation, muscle tone, respiratory effort
  • Each component is given 0–2 points, depending on the status of the newborn.
  • The total Apgar score is the sum of all five components.
• Assessing the need for and beginning neonatal resuscitation should be done independently of and before the Apgar score is determined
• Assessment of the Apgar score at 5 minutes: infants with scores < 7 may require further intervention
  • Reassuring: 7–10
  • Moderately abnormal: 4–6
  • Low: 0–3
• In infants with a score below 7, the Apgar assessment is performed at 5–minute intervals for an additional 20 minutes.
• Persistently low Apgar scores are associated with long-term neurologic sequelae.

APGAR: Appearance, Pulse, Grimace, Activity, Respirations

The Apgar score is useful for evaluating the status of a newborn infant, but it should not be used to draw conclusions about individual neonatal morbidity or mortality and it should not be used as a long-term prognostic tool.

Neonatal resuscitation ^[10][11]

• High-risk deliveries: should have a team of health care providers experienced in neonatal resuscitation on hand
  • Maternal factors: very advanced maternal age or very young maternal age, diabetes or hypertension, substance abuse, previous fetal loss
  • Fetal factors: prematurity, postmaturity, congenital anomalies, multiple gestations
  • Complications of pregnancy and delivery: placental anomalies, oligohydramnios/polyhydramnios, transverse/breech delivery, chorioamnionitis, meconium-stained amniotic fluid, abnormal fetal heart rate, delivery with forceps/vacuum/cesarean
• Resuscitation steps
  • Preductal pulse oximetry
  • Positive pressure ventilation (bag-mask ventilation) at a rate of 40–60/minute.
    • Indicated if there is inadequate respiratory effort (e.g., gasping, apnea) or a heart rate < 100 bpm
    • Intubation if pressure ventilation is ineffective or compressions are required
    • Restrictive use of supplementary oxygen guided by pulse oximetry ^[10][12]
      • At birth, ventilation should be provided with room air for infants ≥ 35 weeks gestation.
      • Premature infants < 35 weeks gestation can receive FiO₂ 21– 30% initially, titrated to SpO2.
  • Chest compressions
    • Indicated if heart rate is < 60 bpm despite adequate ventilation for 30 seconds
    • Preferably use the two thumb-encircling hands technique if two health care providers are present.
    • Use the two finger technique if only one health care provider is present.
    • 3 chest compressions followed by 1 inflation
  • IV epinephrine if heart rate < 60 bpm despite adequate ventilation and chest compressions for at least 30–60 seconds
  • If there is no evidence of ROSC within 20 minutes, consider termination of resuscitation. ^[10]

Preventive measures directly after birth

• Ophthalmic antibiotics: to prevent gonococcal conjunctivitis (erythromycin ophthalmic ointment)
• Vitamin K: to prevent vitamin K deficiency bleeding of the newborn (VKDB)

Measurement and a detailed examination of the newborn should take place within the first 24 hours of life. See “Clinical relevance” for examples of pathological findings of a newborn examination.

• Measurements ^[13]
  • Normal range (10^th to 90^th percentile at 40 weeks gestation)
  • Length: ∼ 50 cm (48– 53 cm)
  • Weight: ∼ 7½ lb (6 lb, 6 oz to 8 lb, 9 oz (2.9–3.9 kg))
    • Boys: 6 lb, 6 oz to 8 lb, 9 oz (2.9–3.9 kg)
    • Girls: 6 lb, 2 oz to 8 lb, 6 oz (2.8–3.8 kg)
  • Head circumference: ∼ 35 cm (33–37 cm)
• Vital signs ^[14]
  • Respiratory rate: 40–60 breaths per minute
  • Heart rate: 120–160 beats per minute
• Bilirubin: see ”Neonatal jaundice”
• pH: ≥ 7.2 (slightly more acidic than adults) ^[15]
• Urine and meconium ^[16]
  • First passage of urine within 24 hours of birth
  • First passage of meconium; (a black-green, tarry substance that forms the newborn's feces) within 48 hours after birth
• Feeding: encourage and provide counseling regarding breastfeeding
• Losing weight after birth ^[17]
  • Loss of up to 7% of birth weight in first five days of life is normal and no specific treatment is required.
  • Newborns normally regain their birth weight by the time they are 10–14 days old.
  • For causes of small-for-gestational-age infants, see “Intrauterine growth restriction.”
• Consequences of intrauterine estrogen exposure
  • Breast bud development is normal in newborns, independent of sex.
  • Newborn girls may have bloody mucoid vaginal discharge.

The physiological respiratory rate and heart rate of newborns are substantially higher than in adults and older pediatric patients.

Healthy newborns normally lose up to 7% of their original birth weight in the first 5 days of life. This weight is then gained back through drinking breast milk and/formula by age 10–14 days. No treatment is necessary.

External signs of maturity

• Skin color and texture: rosy
• Body hair: lanugo may be present, thinning, or mostly absent
• Eyes: open
• Ears: well-formed pinna (auricular cartilage) that instantly recoils
• Breast: clearly discernible areola
• Testicles: descended
• Labia: labia minora covered by labia majora
• Plantar creases: cover the entire soles of the feet

• Definition: venous hematocrit (HCT) greatly exceeding normal values for gestational and postnatal age
• Epidemiology: 1–5% of newborns ^[18]
• Risk factors
  • SGA
  • LGA
  • Infants of diabetic mothers
  • Twin-to-twin transfusion syndrome (recipient)
  • Maternal tobacco use
  • Chromosomal abnormalities
  • Delayed umbilical cord clamping
• Pathophysiology
  • Delayed umbilical cord clamping → erythrocyte transfusion → ↑ circulating red blood mass (HCT)
  • Placental insufficiency or chronic intrauterine hypoxia → increased intrauterine erythropoiesis → ↑ circulating red blood mass (HCT)
• Clinical features
  • Respiratory distress, cyanosis, apnea
  • Poor feeding, vomiting
  • Hypoglycemia
  • Plethora
  • Lethargy and irritability
  • Tremors or seizures
• Diagnostics
  • Venous HCT > 65%
  • Hemoglobin > 22 g/dL
• Treatment (if symptomatic)
  • Monitoring
  • IV hydration
  • Partial exchange transfusion: a procedure in which part of the blood is replaced with an isotonic fluid to lower the hematocrit
    • Indicated in asymptomatic patients with high hematocrit (> 75%) or symptomatic patients with hematocrit > 65% ^[19]
    • Increased risk of NEC ^[20]
• Complications
  • Hypoglycemia
  • Hyperbilirubinemia
  • NEC

Erythema toxicum neonatorum

• Definition: : a benign, self-limiting rash that appears within the first week of life
• Etiology: unknown (probable contributing factors: immature sebaceous glands and/or hair follicles)
• Clinical features
  • Small, red macules and papules that progress to pustules with surrounding erythema
  • Located on trunk and proximal extremities
  • Spares the palms of hands and soles of feet
• Diagnostics
  • Based on clinical appearance of rash
  • Biopsy or smear of pustula (rarely necessary): ↑ eosinophils
• Treatment: observation only
• Prognosis: : typically resolves without complications within 7–14 days

Congenital dermal melanocytosis (Mongolian spot)

• Definition: benign blue-gray pigmented skin lesion of newborns
• Neonatal prevalence ^[21]
  • Asian and Native American: 85–100%
  • African American: > 60%
  • Hispanic: 46–70%
  • White: < 10%
• Pathophysiology: melanocytes migrating from the neural crest to the epidermis during development become entrapped in the dermis
• Clinical features
  • Blue-gray pigmented macule (may also be green or brown)
  • Diameter: typically < 5 cm, may be > 10 cm
  • Location: most common on the back; , also seen on the buttocks; , flanks, and shoulders
• Diagnostics
  • Based on clinical appearance
  • It is important to document the diagnosis of Mongolian spots, as they may resemble bruises and lead to false suspicions of child abuse.
• Prognosis: : usually resolves spontaneously during childhood (typically by the age of 10 years) ^[22]

Congenital melanocytic nevus

• Epidemiology: 1/20,000 births ^[23]
• Clinical features ; ^[23]
  • Vary in size: < 1.5 cm to > 20 cm
  • A nevus larger than 20 cm in size is referred to as a giant congenital melanocytic nevus
  • Light to darkly pigmented lesion
  • Often with increased hair growth
• Treatment: surgical excision or laser ablation (depending on type and size of lesion)
• Prognosis: large nevi are at risk of degeneration → frequent follow-up

Infantile hemangioma (strawberry hemangioma)

• Definition: benign capillary vascular tumor of infancy
• Epidemiology
  • Occurs in 3–10% of infants ^[24]
  • Mostly affects girls
• Pathophysiology
  • Abnormal development of vascular endothelial cells
  • Rapid proliferation followed by subsequent spontaneous slow involution (occurring at the age of 5–8 years) ^[25]
• Clinical features
  • Manifests during the first few days to months of life
  • Progressive presentation; : blanching of skin → fine telangiectasias → red painless papule or macule (strawberry appearance)
  • Most commonly on head and neck
  • Usually solitary lesions
• Diagnostics
  • Based on clinical findings
  • The differential diagnosis of cherry angioma is found mostly in adults.
• Treatment
  • Active nonintervention (monitoring, parental education)
  • Systemic therapy with propranolol in complicated cases
    • Rapidly growing cutaneous hemangiomas
    • Periorbital hemangioma: vascular anomaly in the periorbital region, most commonly the upper eyelid
    • Hemangiomas in the airways, gastrointestinal tract, or liver
    • Hemangiomas with high risk of complications
  • If unresponsive to medication
    • Cryotherapy
    • Laser therapy
    • Resection if necessary
• Complications
  • Ulceration
  • Disfigurement
• Prognosis
  • Usually good prognosis
  • Spontaneous resolution is common
  • Visual impairment if periorbital hemangioma is left untreated

Others

• Milia neonatorum
  • Definition: tiny epidermal papules caused by the buildup of keratin and sebaceous secretions
  • Clinical features: pinhead-sized lesions located on the face/trunk
  • Treatment: not necessary
  • Prognosis: benign skin lesion, spontaneous resolution without scarring
• Capillary malformations (naevus flammeus, port-wine stain, firemark)
  • Definition: congenital, benign vascular malformations of the small vessels in the dermis
  • Epidemiology: may occur in association with a neurocutaneous disorder such as Sturge-Weber syndrome
  • Clinical features: typically unilateral, blanchable, pink-red patches that grow and become thicker and darker with age
  • Treatment: cosmetic laser treatment if desired (not necessary)
  • Prognosis: benign skin lesion
• Transient neonatal pustular melanosis (TNPM)
  • Definition: a benign, transient, idiopathic neonatal skin condition
  • Epidemiology ^[26]
    • Incidence: ∼ 2%
    • Most commonly occurs in African American infants (5 %)
  • Clinical features
    • Solitary or clustered pustules and vesicles on a nonerythematous base
    • Hyperpigmented, erythematous macules and collarettes of fine scale
    • Most commonly affects the forehead, anterior neck, and lower back
  • Treatment: reassurance
  • Prognosis: benign, self-limiting skin lesion
• Nevus anemicus
  • Definition: a pale patch of skin that does not create erythema in response to trauma, heat, or cold
  • Etiology: caused by a vascular anomaly (increased sensitivity of cutaneous blood vessels to naturally occurring catecholamines)
  • Treatment: not required
• LEOPARD Syndrome (Noonan syndrome with multiple lentigines)
  • Lentigines: lenticular hyperpigmentation (dark macules)
  • Electrocardiographic conduction abnormalities
  • Ocular hypertelorism
  • Pulmonary stenosis
  • Abnormalities of genitalia
  • Retardation of growth
  • Deafness
  • See “Noonan syndrome” in “Rare inherited syndromes.”
• Neonatal acne
• Blueberry muffin syndrome
  • A descriptive term for neonates born with multiple bluish, purple marks in the skin, which can be due to extramedullary erythropoiesis, purpura, or metastases.
  • The differential includes various cancers (e.g., rhabdomyoscarcoma), blood disorders (e.g., hemolytic disease of the new born), and congenital viral infections (e.g., rubella)

Some congenital infections may manifest with rashes or other skin conditions and should be differentiated from benign skin lesions in the newborn.

• In the US, each state has its own newborn screening program, and the conditions screened for vary from state to state.
• The U.S. Department of Health and Human Services has made some recommendations, for a comprehensive list of recommended uniform screening panels, see the “Tips & links” section.
• Most of the tests are performed on filter paper using a few drops of blood from a newborn's heel.
• Optimal time for screening: 36–72 hours after birth

Examples of commonly screened conditions

• Endocrine conditions
  • Congenital hypothyroidism
  • Congenital adrenal hyperplasia
• Metabolic conditions
  • Disorders of fatty acid metabolism
  • Disorders of organic acid metabolism (e.g., isovaleric acidemia, methylmalonic acidemia, propionic acidemia)
  • Disorders of amino acid metabolism; (e.g., phenylketonuria, homocystinuria, maple syrup urine disease, citrullinemia type I)
• Hemoglobinopathies (e.g., sickle cell disease, beta thalassemia)
• Other conditions
  • Hearing loss (otoacoustic emissions and/or auditory brainstem response)
  • Critical congenital heart defects
  • Cystic fibrosis
  • Classical galactosemia
  • Severe combined immunodeficiencies (SCID)
  • Glycogen storage disease type II (Pompe disease)
  • Mucopolysaccharidosis type I
  • X-linked adrenoleukodystrophy
  • Spinal muscular atrophy
  • Biotinidase deficiency
    • Etiology: metabolic disorder that leads to biotin deficiency
    • Clinical features: dermatitis, CNS damage
    • Treatment: biotin substitution

Head

• Head molding
• Caput succedaneum
• Cephalohematoma
• Subgaleal hemorrhage
• Bulging fontanelles as a sign of increased intracranial pressure
• Facial nerve palsy due to birth trauma

Eyes

• Retinopathy of prematurity
• Newborn conjunctivitis
• Leukocoria (may indicate retinoblastoma)

Ear, nose, and mouth

• Cleft lip or cleft palate
• Choanal atresia

Neck and clavicles

• Birth-related clavicle fracture
• Infant torticollis

Circulatory system

• Neonatal respiratory distress syndrome
• Cyanotic and acyanotic congenital heart defects

Gastrointestinal tract

• Hirschsprung disease
• Necrotizing enterocolitis
• Vitamin K deficiency bleeding of the newborn

Genitalia

• Congenital adrenal hyperplasia

Trunk, spine, and extremities

• Neural tube defects
• Club foot
• Hip dysplasia
• Brachial plexus injuries

Endocrine organs

• Neonatal hypocalcemia
• Congenital hypothyroidism
• Congenital hypopituitarism
• Congenital hyperinsulinism
• Neonatal diabetes