Recognition of the seriously unwell neonate and young infant

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  • See also

    Febrile child
    Sepsis in neonates
    Acceptable range of physiological variables  

    Key points

    1. Infections are the most likely cause of an unwell neonate (<28 days corrected age) and young infant (<3 months), however several other serious conditions can have similar initial presentations 
    2. A fever in any neonate (>38°C) warrants initial investigation and empiric IV antibiotics
    3. Unwell infants can present with non-specific findings — a period of observation, serial examinations and baseline investigations are often helpful


    • Infection is the most common cause of illness, with urinary tract infections (UTI) the most common bacterial infection 
      • Fever is not always present, and neonates and young infants can present hypothermic (rectal temperature <36.5°C)
    • Neonates and young infants at particular risk include:
      • low birth weight and premature babies
      • those with a known medical condition eg congenital anomaly
      • babies from socially disadvantaged families



    • Irritability
    • Fever
    • Lethargy or increased sleepiness
    • Poor feeding (volume taken in previous 24 hours <50% of normal)
    • Vomiting
    • Apnoea
    • Decreased tone
    • Past history of brief resolved unexplained event (BRUE) or seizures

    Antenatal complications: IUGR, gestational diabetes, congenital abnormality, infections, medication and toxin exposure, previous child with early onset sepsis
    Birth history:  Prematurity, GBS status, perinatal stress, prolonged rupture of membranes, maternal fever, resuscitation requirements
    Poor Growth
    Urine output: <4 wet nappies in 24 hours


    General aspects of the child's behaviour and appearance provide the best indication of whether serious illness is likely

    Features suggestive of an unwell child


    Pallor (including parent/carer report) 


    Lethargy or decreased activity 
    Poor Feeding
    Not responding normally to social cues 
    Does not wake or only with prolonged stimulation, or if roused, does not stay awake 
    Weak, high-pitched or continuous cry


    Increased work of breathing 

    Circulation and Hydration

    Poor feeding 
    Murmur, weak peripheral pulses
    Persistent tachycardia 
    Central CRT ≥3 seconds 
    Dry mucous membranes, reduced skin turgor, sunken fontanelle  
    Reduced urine output / Hypotension


    Bulging fontanelle 
    Neck stiffness 
    Focal neurological signs 
    Focal, complex or prolonged seizures


    Non-blanching rash 
    Fever for ≥5 days 
    Swelling of a limb or joint 
    Not using an extremity
    Distended abdomen

    Adapted from: Feverish illness in children  NICE guideline 2017

    Causes that need to be considered in an unwell neonate and young infant



    Salient Features

     – Bacterial

    UTI / Pyelonephritis
    Others include:

    Fever vomiting, poor feeding

    Skin erythema and tenderness

    Reduced movement of limb

    Fever, tachycardia, tachypnoea, increased work of breathing
    Irritable, nuchal rigidity or bulging fontanelle

    – Viral


    Tachypnoea, increased work of breathing

    Primary HSV – in first 1 month of life

    Skin vesicles (not present in 1/3 of neonates and can be afebrile), seizures.


    Fever, poor feeding, lethargic, snuffly

    Enterovirus or Parechovirus

    Fever, poor feeding, irritable, possible seizures, persistent tachycardia (myocardial involvement)


    Malrotation with volvulus

    Bile-stained vomit

    Pyloric stenosis

    Progressive, non-bilious and projectile vomiting, mass , hypochloraemic hypokalaemic metabolic alkalosis

    Incarcerated hernia

    Irreducible inguinal swelling

    Hirschsprung disease and Meconium ileus

    Abdominal distention with absent or infrequent bowel motions

    Necrotising enterocolitis (NEC):

    Abdominal distention, tenderness, vomiting, blood in stool


    Intermittent severe abdominal pain, vomiting, pallor, lethargy and rectal bleeding (red currant stool)


    Congenital cardiac disease 

    Cyanosis, murmur (not always present), diaphoresis (sweating) with feeding, Cardiac failure (tachypnoea, enlarged liver, hypoperfusion), poor or absent peripheral pulses 

    Supraventricular tachycardia (SVT) and other arrhythmias

    Persistent marked tachycardia, pallor, poor feeding


    Meconium aspiration

    Meconium stained liquor

    Transient Tachypnoea of Newborn and Respiratory Distress Syndrome

    Tachypnoea, increased WOB , possible cyanosis and radiological features


    Tachypnoea, hyperresonance, decreased breath sounds

    Endocrine and Metabolic 

    Congenital adrenal hyperplasia

    Ambiguous genitalia, hypotension, dehydration, hyponatraemia, and hyperkalaemia, hypoglycaemia

    Inborn errors of metabolism

    Coma, hypotonia, seizures, jaundice, organomegaly, dysmorphism
    Hypoglycaemia, metabolic acidosis


    Acute bilirubin encephalopathy


    Non Accidental Injury

    Bruising, unexplained injury 

    Brief resolved unexplained event (BRUE)





    Any neonate and young infant who appears unwell should be assessed promptly and discussed with a senior doctor


    • For unwell neonates and young infants: Perform FBE, CRP, blood culture, urine (SPA), BSL, LP
    • Investigate according to likely cause (see table above)
      • Consider blood gases 
      • Consider chest X-Ray


    • All unwell neonates and young infants should receive:
    • Careful fluid management:
    • Treatment targeted to underlying suspected cause
    • Consider a nasogastric tube on free drainage if bowel obstruction is suspected 
    • Early referral to the paediatric, surgical and/or sub-specialist teams as indicated
    • In neonates with suspected duct dependent congenital cardiac condition, consider IV prostaglandin.

    Consider Consultation with local paediatric team when

    Assessing any unwell neonate or young infant

    Consider transfer when

    Child requiring care beyond the comfort level of the hospital

    For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

    Consider discharge when 

    • The neonate/infant is clinically well and there is low likelihood of infection based on examination and negative infective indices
      • In this setting, and if cultures are negative at 48 hours, antibiotics can be ceased

    Note: a clinically well child (≥3 months) with normal investigations can be discharged with follow up in 12-24 hours

    Parent information sheet

    Fever in children
    Crying and unsettled children
    Urinary tract infections and Urine samples
    Interacting with your baby


    Last updated December 2019

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