• Clinical science

The newborn infant


Infants are usually born “at term,” or after 37 to 42 weeks of gestation. 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 additional 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 terminology

Live birth Presence of vital signs at birth
Miscarriage (spontaneous abortion) Absence of vital signs, pregnancy loss before the 20th week of gestation and fetal weight less than 500 g
Stillbirth (Fetal death)

No uniform definition: absence of vital signs; most US states report fetal death if pregnancy loss during or after the 20th week of gestation and fetal weight more than 500 g

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
Post term infant Live birth later than the 42nd week of gestation
Small-for-gestational-age infant (SGA) Birthweight < 10th percentile
Appropriate-for-gestational-age infant (AGA) Birthweight 10th–90th percentile for gestational age
Large-for-gestational-age infant (LGA) Birthweight > 90th percentile for gestational age
Perinatal period The period from the 22nd week of gestation to the 7th day after birth
Postpartum period First 4–6 weeks after birth
Infant A child under 1 year of age
Newborn A child under 28 days of age


Immediate care and Apgar score

Immediate care of the newborn

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

Apgar score

  • Used for clinical assessment of newborns at 1 and 5 minutes after birth
  • The 1-minute Apgar score is not used to determine the need for neonatal resuscitation, which should begin if necessary before the score is assigned.
  • Assessment of 5-minute Apgar score: infants with scores < 7 may require further intervention
    • Reassuring: 7–10
    • Moderately abnormal: 4–6
    • Low: 0–3

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

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

  • Infants who are born prematurely, lack muscle tone, or are not breathing or crying may require some type of medical intervention.
  • High-risk deliveries should have a health care provider experienced in neonatal resuscitation on hand.
  • Resuscitation steps
    • Begin pulse oximetry
    • Positive pressure ventilation with bag mask
      • Indicated if there is inadequate respiratory effort or a heart rate < 100 bpm
      • Intubation if pressure ventilation is ineffective or compressions are required
    • Chest compressions if heart rate is < 60 bpm despite adequate ventilation for 30 seconds
    • IV epinephrine if heart rate < 60 bpm despite adequate ventilation and chest compressions for at least 30–60 sec

Preventive measures directly after birth


Assessment of the newborn

Measurement and a detailed examination of the newborn should take place within the first 24 hours of life.

  • Measurements
    • Normal range (10th to 90th 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))
      • Head circumference: ∼ 35 cm (33–37 cm)
  • Vital signs
  • Bilirubin: see neonatal jaundice
  • pH: ≥ 7.2 (slightly more acidic than adults)
  • Urine and meconium
    • First passage of urine within 24 hours of birth
    • First passage of meconium within 48 hours after birth
  • Feeding: encourage and provide counseling regarding breastfeeding
  • Losing weight after birth
  • Consequences of intrauterine estrogen exposure

It is important to know that the physiological respiratory rate and the heart rate of newborns are substantially higher than in adults and even other pediatric patients!

Healthy newborn infants 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/or 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


Neonatal polycythemia

  • Definition: venous hematocrit (HCT) greatly exceeding normal values for gestational and postnatal age
  • Pathophysiology
  • Risk factors
  • Clinical features
  • Diagnosis: : Venous HCT > 65%
  • Treatment (if symptomatic)
    • Monitoring
    • IV hydration
    • Possible partial exchange transfusion (PET)
  • Complications


Neonatal skin lesions

Erythema toxicum neonatorum

  • Definition: erythema toxicum is 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
  • Diagnosis
    • 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:
    • Asian and Native American: 85–100%
    • African American: > 60%
    • Hispanic: 46–70%
    • White: < 10%
  • Pathogenesis: 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
  • Diagnosis
    • 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 5)

Congenital melanocytic nevi

  • Epidemiology: 1/20,000 births
  • Clinical features
  • Treatment: surgical excision or laser treatment (depending on type and size of lesion)
  • Prognosis: Large nevi are at risk of degeneration → frequent follow-up

Infantile hemangioma (strawberry hemangioma)

  • Definition: benign vascular tumors of infancy
  • Epidemiology
    • Occurs in up to 10% of infants
    • Mostly affects girls
  • Pathophysiology
    • Abnormal development of vascular endothelial cells
    • Rapid proliferation followed by subsequent spontaneous slow involution
  • Clinical features
    • Manifests during the first few days to months of life
    • Progressive presentation; : blanching of skin → fine telangiectasiasred painless papule or macule (“strawberry appearance”)
    • Most commonly on head and neck
    • Usually solitary lesions
  • Diagnosis
    • Based on clinical findings
    • The differential diagnosis of cherry angioma is found mostly in adults.
  • Treatment
    • Active non-intervention (monitoring, parental education)
    • Systemic therapy with propranolol in complicated cases:
    • If unresponsive to medication:
      • Cryotherapy
      • Laser therapy
      • Resection if necessary
  • Complications
    • Ulceration
    • Disfigurement
  • Prognosis
    • Usually good prognosis
    • Spontaneous resolution is common (70% by age 7)
    • Visual impairment in untreated periorbital hemangioma



Newborn screening

In the US, each state has its own newborn screening program, and the conditions screened for vary from state to state.