The newborn infant

Last updated: July 21, 2023

Summarytoggle arrow icon

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.

Newborn terminologytoggle arrow icon


Timing of birth [5]

Evaluation of birth weight

Pregnancy loss

Immediate care and Apgar scoretoggle arrow icon

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.
Calculation of the Apgar score
0 Points 1 Point 2 Points
Appearance (skin color) Blue (cyanotic) or pale Pink trunk, blue extremities (acrocyanosis) Pink body and extremities
Pulse (heart rate) None < 100 beats/min ≥ 100 beats/min
Grimace (reflex irritability upon tactile stimulation) None Grimace Cry or active withdrawal
Activity (muscle tone, movement) No movement, limp body Some flexion Active motion, flexion
Respirations None Weak cry, irregular/slow/weak breathing or gasping Regular breathing, strong cry

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]

Preventive measures directly after birth

Assessment of the newborntoggle arrow icon

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 (10th to 90thpercentile 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]
  • 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]
  • Consequences of intrauterine estrogen exposure

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

Gestational age is estimated at birth with the Ballard score, which combines neuromuscular assessment with the following physical signs of maturity: [18]

Examination for abnormalities

For an overview of potential examination findings, see “Clinically relevant neonatal conditions.”

Face and head [18]

Intermittent strabismus is a normal finding in children < 4 months of age. [20]

Spine and nervous system [21]

Thorax [18][21]

Abdomen [21]

  • Check that the abdomen is not distended or scaphoid.
  • Palpate the abdomen for masses and organomegaly.
  • Auscultate for bowel sounds.
  • Check the umbilical cord.
    • Ensure there are two arteries and one vein; a single umbilical artery can be associated with other congenital abnormalities.
    • Look for signs of bleeding/infection.

Genitourinary examination [21]

Extremities [21]

Skin [21]

Newborn screeningtoggle arrow icon

  • Before leaving the hospital, newborns should be screened for serious and life-threatening conditions.
  • The optimal time for screening is 24–48 hours after birth. [23]
  • Screening usually involves assessment for:
    • Critical congenital cardiac defects
    • Hyperbilirubinemia
    • Congenital deafness
    • Various genetic disorders, e.g., endocrine, metabolic, and hematological disorders

Which genetic disorders to screen for varies according to national and state law; check local guidelines.

Overview of screening for newborns [24][25]

Newborn recommended screening [24][25]
Conditions to screen Recommended ages Method of screening Actions for abnormal findings
Congenital metabolic or hematological disorders
  • At birth and, in some states, again at 2 weeks of age
  • Follow state-mandated recommendations on newborn screening.
  • In most cases, a capillary heel stick is used to collect dried blood spot samples on filter paper.
  • Follow Act Sheet recommendations.

Critical Congenital Heart Defects (CCHD)

  • At ≥ 24 hours of life and/or prior to nursery discharge
Congenital deafness [26]

Examples of commonly screened genetic conditions

Clinically relevant neonatal conditionstoggle arrow icon




Ear, nose, and mouth

Neck and clavicles

Circulatory system

Gastrointestinal tract

Urogenital system

Trunk, spine, and extremities

Endocrine organs

Hematological system

Neonatal skin lesionstoggle arrow icon

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
  • 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 [28]
    • 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)
    • Location: most common on the back, also seen on the buttocks, flanks, and shoulders
    • Diameter: typically < 5 cm, may be > 10 cm
  • 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) [29]

Congenital melanocytic nevus

  • Definition: a congenital skin lesion caused by the proliferation of melanocytes
  • Epidemiology: 1/20,000 births [30]
  • Clinical features ; [30]
    • Light to darkly pigmented, well-circumscribed macule or patch
    • Often with increased hair growth
    • 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
  • 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 [31]
    • More commonly affects girls
  • Pathophysiology
  • 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
  • Complications
  • Prognosis
    • Usually good prognosis
    • Spontaneous resolution is common
    • Visual impairment if periorbital hemangioma is left untreated


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

Physiologic anemia of infancytoggle arrow icon

Neonatal polycythemiatoggle arrow icon

Neonatal hypoglycemiatoggle arrow icon

Macrosomiatoggle arrow icon

Referencestoggle arrow icon

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